the molluscan fauna of the alum bluff group of florida

166 THE MOLLUSCAN FAUNA OF THE ALUM BLUFF GROUP OF FLORIDA
the second species is closely allied to Antigona blandiana
(Guppy), of the Bowden beds of Jamaica.
Concentric lamellae crenulated, recurved toward the um-
bones______ ____ ______________ Antigona caesarina (Dall).
Concentric lamellae simple, not recurved toward the urn-
bones. _____ _______ Antigona sp. cf. A. blandiana (Guppy).
Subgenus ANTIGONA s. s.
Type: Antigona lamellaris Schumacher. (Recent
in the Indo-Pacific.)
Dall u describes this subgenus as follows:
Shell large, reticulately sculptured; the portion of the
escutcheon in the right valve (when not defective) forming a
thin lamina which projects over the sunken ligament and
almost completely hides it; pallia! sinus wide, short, and rather
rounded in front; lateral tooth minute or obsolete.
Antigona caesarina (Dall)
Plate XXV, Figure 22
1903. Cytherea caesarina Dall, Wagner Free Inst. Sci. Trans.,
vol. 3, pt. 6, p. 1275, pi. 53, fig. 5.
Dall describes this species as follows:
Shell ovate, inequilateral, the beaks being in or at the anter­
ior fourth; lunule hardly impressed, concentrically striate, cor­
date, small; escutcheon long and narrow, wider in the right
valve, bordered on each valve with a strong sulcus, the ligament
hidden by the right-hand portion; sculpture of numerous narrow,
elevated, thickened, concentric lamellae, somewhat reflected
and with narrower concentrically striate interspaces; these
cross fine radial riblets, which are distinct and uniform on the
young shell but rapidly become obsolete, though the broad tops
of the concentric sculpture are crenulate or, more strictly speak­
ing, articulated by the development on them of channels or
sulci corresponding to those of the obsolete riblets; hinge strong,
the larger cardinals deeply bifid, the anterior lateral small and
pustular; pallial sinus small, ample, short, rounded in front;
inner basal margins minutely crenulate. Length of figured
valve 66, height 58, double diameter 40 millimeters; length of an
internal cast from White Beach 75, height 60, diameter 46 milli­
meters.
This fine species is quite distinct from any of the others; the
radial sculpture, contrary to usage, is more distinct in the mid­
dle of the disk than on the distal portions of the shell. It much
more nearly resembles the recent west American C. multicostata
Sowerby than any species now living on the Atlantic side and
adds in this way an interesting item to the list of those which
indicate more or less clearly a tolerably close connection between
the two faunas in Oligocene [Miocene] times.
Type: U. S. Nat. Mus. No. 114754.
Type locality: No. 2212, Tenmile Creek, 1 mile west
of Baileys Ferry, Calhoun County, Fla.
The casts from White Beach are probably distinct,
and the race is larger than that of the Chipola, the
umbones more inflated, and the outline rudely qu> d-
rangular rather than ovate. The posterior dorsal mar­
gin is not far from horizontal and approximately two-
thirds the width of the shell. The umbones are nearer
to the anterior extremity than in A. caesarina^ and the
base is much less obliquely rounded.
A. caesarina (Dall) is characterized not only by the
large size and obliquely ovate outline, but also by the
" Dall, W. H., op. cit, vol. 3, pt. 6, p. 1272, 1903.
numerous concentric lamellae, with their margins ex­
panded and recurved toward the umbones and crin­
kled like a pie crust.
Occurrence: Chipola formation, locality 2212P.
Section VENTRICOLA Romer
1867. Ventricola Romer, Malakozoologische Blatter, vol. 14,
p. 115.
Type: Chione rugosa (Chemnitz). (Recent in the
tropical waters of the east coast.)
Dall 15 characterizes this group as follows:
Shell large with strong, recurved, concentric lamellae regu­
larly spaced, between which are smaller concentric threads;
pallial sinus small, angular; lunule deeply impressed.
Antigona (Ventricola) n. sp.?
1903. Cytherea (Ventricola) blandiana Guppy. Dall, Wagner
Free Inst. Sci. Trans., vol. 3, pt. 6, p. 1272 (in part).
Not Venus blandiana, Guppy, 1874.
The Antigona (Ventricola} from the Chipola, which
has been referred to blandiana, is known from only a
few fragmentary individuals, but these certainly indi­
cate a species decidedly less inflated and more nearly
orbicular in outline than the Bowden form. The
White Beach specimens are more closely allied to the
Chipola than to the Bowden species, but the material
is too imperfect to permit definite determination.
Occurrence: Chipola formation, localities 2212r,
2213 r
Subfamily VENERINAE Dall
Dall 16 characterizes the subfamily as follows:
The present subfamily is characterized by the total absence
of lateral teeth. The siphons are usually comparatively short
and more or less separate from each other. The foot is hatchet
shaped and, in the adult, not byssiferous except among the
nestlers. The young undergo their development outside of the
parent shell.
Genus CHIONE Megerle von Muhlfeld
1811. Chione Megerle von Muhlfeld, Magazin Gesell. naturf.
Freunde Berlin, vol. 5, p. 51.
Not Chione Desvoidy, 1830 (Diptera).
Not Chione Gray, 1838=MacrocaZ^sto.
Type: Venus dysera Chemnitz = Chione cancellata
(Linnaeus). (Recent off the east coast from Hatteras
to Trinidad.)
Dall 17 describes this genus as follows:
This group contains solid trigonal shells which have three
cardinals in each valve and (excepting a few aberrant species)
have the valve margins entirely crenulate; all have a small
triangular sinus, a lunule circumscribed by an incised line, an
escutcheon not limited by any line and defined chiefly by a
deficiency of coarse sculpture and a more or less pronounced
ridge radiating from the beak toward the posterior margin.
The ligament, though inset, is usually visible externally; some
of the central cardinals may be grooved or bifid; rugosities
appear on the hinge in a few instances. The sculpture is
variable, chiefly comprising concentric ribs or lamellae and less
prominent radials.
» Dall, W. H., op. cit., vol. 3, pt. 6, p. 1272,1903.
n Idem, p. 1281.
»Idem, p. 1287.