translucent. The auricles are low and in the right valve unequal, for the anterior is cut by the byssal notch. The radial sculpture is feeble or absent altogether, but the surface is in many specimens concentrically imbricated. The inner face of the disk is smooth.

Pseudamussium differs from the other Pectens in the absence of a well-defined external sculpture, from Amusium in the absence of strong internal lirae.

The subgenus has been reported from the midMesosoic and is still existent. Though never abundant, Pseudamussium is probably better represented during the Eocene, both in this country and in Europe, than during any other period.

There is a lamentable lack of uniformity in the spelling of the name of this subgenus and the name of the genus to which it bears so strong a superficial resemblance. With the continentals, as a rule, we have Amussium and Pseudamussium; in this country, Amusium and Pseudamusium. I have followed the original spelling of the authors, though Bolten was doubtless incorrect when he wrote the name of the "compass shell" with only one s. The name is derived from the Latin amussium, a horizontal wheel for denoting the direction of the wind.

Pseudamussium defuniak Gardner, n. sp.

Plate XII, Figures 10-12

Shell very small, rather thick, porcellanous, the disk a rude sector of about 90°. Right valve moderately inflated, obliquely flattened toward the umbones. Left valve flattened. Umbones acute, rising a little above the hinge line. Anterior dorsal margins acutely angulated, slightly more produced than the obtusely angulated posterior margins. Surface of disk smooth except for exceedingly faint traces of a striation like that of Camptonectes, visible only under high magnification on a single individual. Traces of a blotchy color pattern also discernible. Auricles rather small, those of the left valve subequal, the anterior auricle of the right valve higher and more produced than the posterior; anterior auricle cut off from the disk by a narrow but well-defined byssal groove. Margin sharply elevated along the groove and outlined by an obscure thread; traces of one or two more threadlets and a feeble concentric lamination commonly visible near the notch; right posterior auricle not sharply differentiated from the disk and apparently free from sculpture; left anterior auricle and submargin shagreened with an exceedingly fine concentric lamination and radial threading, which becomes obsolete toward the hinge; left posterior auricle and submargin merging smoothly into one another and into the disk, faintly lineated away from the hinge line but showing no trace of a concentric imbrication. No trace of a ligament area along the hinge margin. Resilial pit minute; provinculum still retained on all

the hinge margin, the ventral margin of the provinculum expanding slightly about halfway between the ligament pit and the distal extremities of the hinge. Adductor scar very obscure, apparently rather small, quite strongly posterior, and about midway between the dorsal and ventral margins. Pallial line also obscure. Inner surface of valve smooth.

Dimensions: Altitude of right valve, 3.8 millimeters; left valve of another individual, 4.6 millimeters. Latitude of right valve, 3.75 millimeters; left valve, 4.6± millimeters.

Cotypes: U. S. Nat. Mus. No. 352453. Type locality: No. 5618, 31/1⁄2 miles southwest of De Funiak Springs, Walton County, Fla.

The relationship of this small form to P. guppyi Dall is certainly very close, but it is smaller, the right valve is less convex and the left valve more flattened than in guppyi. The dorsal margins are also less sharply defined as a rule. The Camptonectes sculpture has been observed on only a single individual of defuniak and very obscurely on that, and the ventral expansion of the provinculum is not so marked as in guppyi. The single valve from Oak Grove, which was referred by Dall to guppyi, is possibly specifically identical. The threading upon the auricles is less fine, however, and not so restricted as in defuniak. Occurrence: Shoal River formation, localities 7264", 10608г, 5618P.

Pseudamussium diktuotum Gardner, n. sp.
Plate XII, Figures 13-14

Shell small, relatively thick, porcellanous; the disk a rude sector of about 90°. Right valve moderately inflated, obliquely flattened toward the umbones; left valve compressed. Umbones acute, projecting a little beyond the hinge line. Anterior extremity slightly more produced than the posterior. External surface covered with a crowded, microscopically fine threading crossed by sharp and regular incrementals, thus forming a rather regular reticulate sculpture. Auricles small, those of the left valve not so small as those of the right; anterior auricle of left valve more sharply differentiated from the disk than the posterior auricle; anterior auricle of the right valve larger than the posterior and more sharply threaded, cut off from the disk by a shallow but distinct byssal notch; Resilial pit minute. Provinculum still retained in the form of fine ridges normal to the hinge margin, expanding slightly midway between the resilial pit and the distal extremities of the hinge. Adductor scar obscure, posterior in position. Pallial line ill defined. Inner margins smooth.

Dimensions: Altitude of right valve, 3.8 millimeters; left valve of another specimen, 4.2 millimeters. Latitude of right valve, 4.0 millimeters; left valve of another specimen, 4.5 millimeters.

Cotypes: U. S. Nat. Mus. No. 352454.

There is a considerable degree of variation in the strength of the sculpture upon this remarkable little species. On some specimens the sculpture is almost obsolete, on others it is very sharply and evenly reticulate. However, the development of any sculpture other than the Camptonectes striation upon the disk is sufficient to distinguish this species from all the other east coast Tertiary forms.

Occurrence: Oak Grove sand, locality 9961P.

Pecten (Pseudamussium) sp.

1898. Pecten (Pseudamusium) guppyi Dall, Wagner Free Inst. Sci. Trans., vol. 3, pt. 4, pp. 718, 755 (part).

Type locality: No. 2580, Bowden, Jamaica.

The single left valve from Oak Grove which has been included under this species differs from the Bowden forms in its lower, broader outline, the less fine and more even threading of the auricles, and the apparent absence of the Camptonectes striation upon the disk. It is smaller, too, than the Bowden individuals and quite possibly immature. Further material must be collected before the species is sufficiently well known to determine. It may quite possibly prove to be identical with the valves of similar dimensions and outline collected from the Shoal River in the environs of De Funiak Springs. The threading upon the auricles of the Shoal River individuals is even finer than that on the Oak Grove valve and becomes obsolete altogether near the hinge line.

Occurrence: Oak Grove sand, locality 2646."

Genus AMUSIUM Bolten

1798. Amusium Bolten, Museum Boltenianum, 1st ed., pt. 2, p. 165.

Type: Ostrea pleuronectes Linnaeus. (Recent in the Indo-Pacific.)

The valves are commonly large, thin, and feebly convex and like those of the true Pectens are not attached by a byssus. Radial sculpture is sometimes suggested by the color pattern but is rarely developed and is never strong. A concentric imbrication may be observed in some species, particularly toward the ventral margin. The discrepancy in ornamentation so.common in Pseudamussium is reflected in the discrepant coloring in Amusium s. s. In Amusium papyraceum, the Recent Antillean shell, the right valve is white or bordered with pale yellow, but the left is a deep reddish or purplish brown. This general type of color holds throughout Amusium s. s. The lirae developed upon the inner surface of the disk are perhaps the most constant diagnostic of the genus.

Like Pecten, Amusium may be traced back to the Mesozoic. The thin, internally lirate shells of

than the heavy, externally ribbed shells of most of the Pecten group, and perhaps for this reason the genus is relatively rare.

P. precursor is nearly as large as P. mortoni, but slightly rougher and more convex when adult, the young are nearly orbicular; a distinct trace of Camptonectes striation, near the beak and submargins, may be discerned with a magnifier in a good light. Altitude 110, latitude 123, diameter 20 millimeters. The right valve is much flatter than the other. As the material is much broken up, it seemed hardly worth while to figure it.

Type: U. S. Nat. Mus. No. 114773. Type locality: No. 2212, Tenmile Creek, 1 mile west of Baileys Ferry, Calhoun County, Fla.

Fragments are common at the localities on Chipola River, but no perfect adult has yet been brought back. A faint radial lineation may be discerned upon the auricles as well as upon the umbone, but this character as well as most of the others is shared by P. mortoni.

Occurrence: Chipola formation, localities 2212o, 2213°, 2564 P.

Family SPONDYLIDAE

Genus SPONDYLUS Linnaeus

1758. Spondylus Linnaeus, Systema naturae, 10th ed., p. 690.

Type: Spondylus gaederopus Linnaeus. (Recent in the Mediterranean.)

Shell inequivalve, subequilateral, ovate or ovatetrigonal in outline, auriculate, normally attached by the right valve, which is, as a rule, more inflated than the left. Surface radially sculptured, the costals commonly unequal and irregular and bearing foliaceous or spinose processes. Auricles smaller and less sharply defined than those of Pecten. Cardinal area higher in the right valve than in the left. Ligament alivincular, lodged in a trigonal slit beneath the umbones. Dentition typically isodont, the teeth two in number in each valve, diverging and interlocking with the teeth of the opposite valve. Only a single adductor scar retained in the adult. Pallial line simple.

Spondylus has been found in strata as old as the Jurassic and still persists in the tropical and subtropical waters. Though never a prolific group, the thorny oysters are conspicuous for their rather large size, elaborate ornamentation, and gorgeous coloring. Only a single species is definitely recognized in the Alum Bluff, a form closely allied to the Spondylus bostrychites of Guppy from Santo Domingo and the Bowden beds.

Spondylus sp. cf. S. bostrychites Guppy

Fragments of a Spondylus collected at a single locality in the Shoal River, indicate a species more closely allied than the Chipola specimens to S. bostrychites Guppy and possibly identical with it.

Spondylus chipolanus Dall

1898. Spondylus bostrychites var. chipolanus Dall, Wagner Free Inst. Sci. Trans., vol. 3, pt. 4, p. 758.

1915. Spondylus chipolanus Dall, U. S. Nat. Mus. Bull. 90, p. 125, pl. 19, fig. 1 (part).

Dall described this species in 1898 as follows: The type form of this species has a relatively small number of spinose ribs, the intervening ones being free from spines, longitudinally finely striate, and show when very perfect minute scales. The adult shell is rather short and rounded and less inflated than usual in the genus. The species is remarkable for its small hinge area.

In the variety chipolanus Dall there is no radial striation on the interspatial ribs, but rather a concentric sculpture; there are many more spinose ribs, the shell is more oval and more inflated, and, as far as the material goes, seems to attain a larger size. It may prove distinct with more perfect specimens, in which case the varietal name may be taken as specific.

Type: U. S. Nat. Mus. No. 114817.

Type locality: No. 2213, 1 mile below Baileys Ferry, Calhoun County, Fla.

The Chipola species attains considerable dimensions, imperfect double valves showing an altitude of 110.0± millimeters, a latitude of 85.0 millimeters, and a maximum diameter of 65.0 millimeters. The right valve is quite strongly rounded, the left valve inflated or flattened. The sculpture is exceedingly variable in detail but invariably ornate. The surface is crowded with unequal radial threads, all of them more or less spiny and every third or fourth thread heavier than the others and bearing long, slender spinose processes. The concentric imbrication is very close and for the most part microscopically fine. The cardinal area is higher in the right valve than in the left and slit medially by the ligament, which extends from the tip of the umbones to the ventral margin of the hinge, expanding slightly ventrally. The teeth are short, very thick and heavy, and slightly hooked at their extremities. The teeth of the right valve are inclosed in sockets formed by the elevated margins of the ligament pit of the left valve and the inner surface of the teeth. The muscle scar is very large, roundish, and placed a little behind and ventral to the middle.

The species that occurs at Ballast Point is apparently the true bostrychites of the West Indies, The specimen figured in Bulletin 90 is from Chipola River and is the type of S. chipolanus. The very young right valves are sculptured with overlapping concentric laminae, quite unlike anything exhibited by the adult.

Occurrence: Chipola formation, localities 2212, 2213P, ?2211. Oak Grove sand, locality ?26465.

Occurrence: Shoal River formation, localities, 9957",

10603г.

Genus PLICATULA Lamarck

1801. Plicatula Lamarck, Système des animaux sans vertèbres, p. 132.

Type: Plicatula gibbosa Lamarck=P. ramosa Lamarck. (Recent on the east coast from Hatteras to Bahia, Brazil.)

Shell inequivalve, flattened or slightly convex, trigonal to subcircular, commonly irregular, attached by the umbone of the right valve, which is the larger. Exterior surface generally plicate. Ligament internal, lodged in a central cartilage pit between the two heavy, divergent, transversely striated cardinal teeth. Pallial line entire. Muscular impression simple, excentric.

The genus originated in the early Mesozoic, culminated in the late Mesozoic, and is represented by less than a dozen recent species, living for the most part in the Pacific and Indian oceans.

Plicatula is separated from its near relative, Spondylus, by the absence of auricles.

Plicatula is not uncommon in the Chipola, rare in the Oak Grove, and unknown in the Shoal River. P. lepidota is known from a single individual. The other of the two Alum Bluff species, P. densata Conrad, can not be separated from the specimens included under that name from the older "silex beds" nor from those occurring in the younger Chesapeake of New Jersey, Maryland, and Virginia.

Surface strongly and regularly plicated radially.

Plicatula densata Conrad. Surface irregularly sculptured both radially and concentrically, not regularly plicate Plicatula lepidota Gardner, n. sp.

Plicatula densata Conrad

Plate XIII, Figures 1-3

1843. Plicatula densata Conrad, Acad. Nat. Sci. Philadelphia Proc., vol. 1, p. 311.

1845. Plicatula densata Conrad, Fossils of the Tertiary formations of the United States, p. 75, pl. 43, fig. 6.

1863. Plicatula densata Conrad, Acad. Nat. Sci. Philadelphia

Proc. for 1862, p. 582.

1895. Spondylus inornatus Whitfield, U. S. Geol. Survey Mon., vol. 24, p. 34, pl. 5, figs. 1, 2.

1895. Plicatula densata Conrad. Whitfield, U. S. Geol. Survey

Mon., vol. 24, p. 35, pl. 5, figs. 3-8.

1898. Plicatula densata Conrad. Dall, Wagner Free Inst. Philadelphia Trans., vol. 3, pt. 4, p. 763.

1904. Plicatula densata Conrad. Glenn, Maryland Geol. Survey, Miocene, p. 371, pl. 98, figs. 7-9.

Conrad described this species in 1843 as follows: Ovate, thick, profoundly and irregularly plicated; inferior valve ventricose, its ribs acute, with arched spiniform scales; cardinal teeth large, curved, laterally striated, crenulated on the margins; larger cardinal tooth in each valve slightly bifid, broad; muscular impression prominent. Length 18 inches. Locality: Cumberland County, N. J.

The valves have about ten folds, and the lower valve resembles a variety of Ostrea virginiana.

The animal may be attached by either the right or the left valve, and over the area of attachment the sculpture is of course obsolete. The form consequently differs greatly, not only in outline but in the character of the sculpture, according to the size and shape of the object to which it is fastened. In the free valves the plications are produced almost to the umbones, but in those fixed valves that are attached over a large area the radial plications are commonly reduced to a narrow frill around the outer margin. The inner surface included within the pallial line is chalky white, except for the vitreous muscle scar.

Plicatula densata is the common member of the

genus in the Alum Bluff fauna. Its nearest relative is the even more strongly plicated species Plicatula marginata Say, so abundant throughout the Miocene of Virginia and the Carolinas. In that form the radial plications range from 3 to 8 and are less prone to ramify and become spinose than in densata. In P. lepidota Gardner, n. sp., known only from a single individual, there is no well-defined radial plication of the valve but only a fine and very irregular surface ornamentation.

Occurrence: Chipola formation, localities 7893P, 2212P, 2213°, 9994, 4986; Oak Grove sand, localities 2646P, 7054г, 9961P.

Outside occurrence: Miocene, "Tampa silex beds," Florida. Calvert formation, New Jersey and Maryland. St. Marys formation, Virginia and North Carolina. Yorktown formation, Virginia and North Carolina.

Plicatula lepidota Gardner, n. sp.
Plate XIII, Figure 11

Shell of moderate dimensions for the genus, rather thin, warped, compressed and angular toward the hinge, broadly expanded ventrally. Only the left valve and the cardinal area of the right known. Cardinal area high and trigonal in the right valve, extremely narrow in the left. Anterior margin of left valve finely serrate just below the hinge line. Surface sculptured with finely crinkled lamellae fluted at more or less regular intervals but not with sufficient regularity to form a well-defined radial sculpture. Only the ventral row of flutings regular in the type and these partly closed and produced into about 15 somewhat spinose processes. Inner margins crenulate. Ligament internal, lodged in a small pit sunk deep beneath the umbones. Dentition vigorous, the teeth of the right valve included between those of the left, the anterior tooth a little heavier than the posterior; sides of all the teeth transversely ridged. Monomyarian,

the single muscle scar very sharply defined, roundish, posterior, and a little below the median horizontal. Pallial line simple, distinct. Surface within the pallial line chalky white except for the vitreous muscle scar. Dimensions: Altitude, 29.5 millimeters; latitude, 30.0 millimeters.

Type: U. S. Nat. Mus. No. 352446.

Type locality: No. 2213, 1 mile below Baileys Ferry, Chipola River, Calhoun County, Fla.

Unlike that of the common, coexistent P. densata, the surface of P. lepidota is not radially plicate but is ornamented with a curiously irregular sculpture not unlike that of some of the oysters. The concentric lamellae are irregular in width and spacing and are roughened by a microscopically fine, irregular grooving, not continuous as a rule, across the free edge. At irregular intervals the edges are sharply fluted, though upon the outermost laminae the flutings are approximately equisized and equispaced. The peculiar roughened, more or less prickly surface of this species is unlike that of any known member of the genus. The type is unique.

Occurrence: Chipola formation, locality 2213г.

Family LIMIDAE

Genus LIMA (Bruguière) Cuvier

1798. Lima Cuvier, Tableau élémentaire de l'histoire naturelle des animaux, p. 421.

Type: Ostrea lima Linnaeus. (Type probably a recent shell from the Mediterranean; widely distributed in nearly all the tropical and south temperate seas; reported fossil in the Pliocene and Pleistocene.)

Shell auriculate, auricles unequal. Outline usually ovate, scoop-shaped and obliquely truncated laterally. Valves closed inferiorly but gaping anteriorly and sometimes posteriorly. Exterior surface rarely smooth, generally sculptured with simple or imbricated radial striae. Umbones rather prominent and distant. Hinge edentulous. Ligament internal, lodged in a subumbonal pit. Pallial line simple. Single muscle scar excentric, nearer to the posterior than the anterior margin.

The genus is indicated in the Carboniferous, culminates in the Cretaceous, and is sparsely represented in nearly all the recent seas by white or colorless shells, which may be attached by a byssus or may swim freely with a motion similar to that of Pecten.

Fragments sufficiently well preserved to establish the presence of the genus in the Alum Bluff have been collected, but their specific identity is uncertain.

Subgenus LIMA s. s.

Type: Ostrea lima Linnaeus. (Recent in nearly all the tropical and south temperate seas; reported fossil in the Pliocene and Pleistocene.)

Lima s. s. is characterized by the gaping, inequilateral valves and the edentulous hinge.

Section MANTELLUM Bolten

1798. Mantellum Bolten, Museum Boltenianum, pt. 2, p. 160. Type: Ostrea inflata Gmelin. (Recent in the Mediterranean Sea; reported from the Pliocene of Italy by Sacco.)

Mantellum is characterized by the widely gaping anterior margins and the submargins which are not impressed like those of the typical section.

Lima hians (Gmelin), which is commonly cited as the type of Mantellum, is not included in Bolten's list of 1798.

Lima (Mantellum) carolinensis Dall

Plate XIII, Figure 4

1898. Lima (Mantellum) carolinensis Dall, Wagner Free Inst. Sci. Trans., vol. 3, pt. 4, p. 767, pl. 35, fig. 21.

Dall described this species as follows:

Shell small, thin, inflated, oblique, with a moderate gape, sculptured with concentric lines of growth and rather sharp, fine, numerous, somewhat irregular radial threads, obsolete on the beaks, absent from the posterior submargin and the anterior ears; submargins not impressed, beak prominent, ears small, the margin of the gape forming a concave sinuosity in front of and below the anterior beak; hinge line short, with a very wide pit, its lower margin projecting from the cardinal plate; interior radially striate, the basal margin slightly crenulate. Altitude 16, latitude 12, diameter 7 millimeters.

This differs from L. papyria Conrad, from the Maryland Miocene, in the absence of the angle which in the latter species modifies the margin just below the anterior ear and in the presence of dense radial striation on the anterior submargin, while in L. papyria this region is smooth.

Type: U. S. Nat. Mus. No. 107801.

Type locality: No. 2025, Darlington, S. C. (Miocene: Duplin formation.)

The Oak Grove individuals are all imperfect, and most of them are immature. Though it is possible that perfect adults might exhibit characters which would be of systematic value in separating them from the Carolina specimens, there are none preserved in the available material.

Occurrence: Oak Grove sand, locality ?2646 P. Outside occurrence: Miocene: Duplin formation, Natural Well, Duplin, N. C., and Darlington, S. C.

Superfamily ANOMIACEA
Family ANOMIIDAE

Genus ANOMIA (Linnaeus) Müller

1758. Anomia Linnaeus, Systema naturae, 10th ed., p. 700 (part).

1776. Anomia Müller, Zoologiae danicae, prodromus seu animalium, p. 248.

Type: Anomia ephippium Linnaeus. (Recent from the Arctic Ocean, off the European shores, to the Aegean archipelago; fossil in the Pliocene of England and Italy and the Pleistocene of Scandinavia.)

Shell inequivalve, adherent, generally subcircular or oblong. Left valve more or less convex, right valve

flattened. Hinge margin of left valve commonly incurved and slightly thickened. Ligament scar found directly beneath left umbone. Interior of disk of left valve scarred with an adductor and a major and minor byssal impression, the major byssal scar being the largest of the three and dorsal to the adductor and minor byssal scars, which are usually subequal; interior of right valve containing foraminal opening and, ventral to it, the impression of the adductor muscle; posterior dorsal margin of right valve carrying an inconspicuous ligamental process. Pallial line simple.

Ancestral forms of this genus have been recognized in rocks as ancient as the Devonian. The recent species number about forty and are widely distributed along the shores from low water mark to 100 fathoms.

Anomia has four representatives in the Alum Bluffthree of them restricted to the Chipola and the fourth, A. floridana, common to the Oak Grove and the Shoal River. Only a single species, however, has been recorded from Chipola River, the A. microgrammata of Dall, a form separated only varietally from a not uncommon Bowden species. A. glypta, from Boynton Landing on the Choctawhatchee, is closely allied to microgrammata. The Suwannee River species, however, has much the aspect of Carolia, though it seems to differ in the characters diagnostic of that genus. External surface very finely and closely lirate or sulcate: Altitude normally exceeding 25.0 millimeters.

Anomia glypta Gardner, n. sp. Anomia microgrammata Dall. External surface smooth or more or less irregularly lirate or plicate:

Altitude not normally exceeding 25.0 millimeters.

Altitude not normally exceeding 40.0 millimeters; color
greenish---
--- Anomia floridana Dall.
Altitude normally exceeding 40.0 millimeters; color chalky
white___
--Anomia suwanneensis Gardner, n. sp.

Anomia glypta Gardner, n. sp.

Plate XIII, Figures 6-7

Shell of moderate dimensions for the genus, thin, subcircular in outline, the left valve warped into a feeble convexity. Umbones distinct but not conspicuous, the tips placed just within the cardinal border and slightly opisthodetic. Surface crowded with a very fine and somewhat irregular radial lineation or grooving similar in a way to that of A. microgrammata Dall but more crowded and less uniform, equally developed, however, on all parts of the disk. Ligament internal, mounted on a low shelly process somewhat reniform in outline, the convex surface parallel to the dorsal margin, the distal extremities more elevated than the medial portion. Hinge edentulous, the cardinal border slightly thickened and arching over the ligament pit. Scarred area elongated dorsoventrally, widening toward its ventral margin, which falls a little below the median horizontal; major byssal scar of approximately the same size and almost directly above the single adductor impression; the minor