114 
cular impressions, extending nearly all along the arch of the 
cardinal margin ; pallial impression interrupted, but destitute of 
a sinus; ligament external, linear, expanded over the outer 
surface of the cardinal facets; cartilage situate in a small, 
short, triangular pit, immediately under the umbones, which 
are slightly prominent. 
}. Gatzomma Turron, pl. XXIII, f. 15, 16. 
Galeomma Turtoni, First Ed., pl. 31, f. 15, 16; Turton, 
Zool. Journ., II, p. 361, pl. 13, f. 1. 
Shell tumid in the middle, compressed towards the extre- 
mities, which are rounded and closed; with a large oval gap at 
the basal margin; hinge destitute of teeth; of a dirty or cream- 
white colour; surface covered with close-set, irregular, trans- 
yerse, interrupted opaque lines; umbones prominent. Length 
two lines and a half; breadth not quite half an inch. 
Dredged in the English Channel, by Dr. Turton. 
Genus 47.—PuHo.as.—Linneus. 
Shell transversely oblong, equivalve, greatly inequilateral ; 
nearly the whole species gaping at both ends, and most of them 
with the opening very large at the anterior end, and extending 
along the basal margin; in some species, however, it is nearly 
closed by a testaceous, almost smooth, somewhat tubular pro- 
longation of the valves; hinge in various species with an une- 
qually sized, small, recurved tooth in each valve; external 
surface generally roughened with muricated striae, presenting a 
rasp or file-like appearance ; most of the species provided with 
a greater or lesser number of accessory valves, situate near the 
fulerum of the hinge, and connected with the shell only by the 
epidermis, which passes over them; each valve furnished with a 
long, curved, flat, tooth-like, testaceous process, projecting from 
the interior of the shell, immediately within the umbones; in 
some species this is expanded, and spoon-shaped; anterior dorsal 
margin near the beaks reflected, close, and flattened down upon 
the umbones in some species, and in others a second margin is 
produced, situate remote from the first, with the intervening 
space divided by a series of transverse septa; two principal 
impressions, formed by the adductor muscle, one of which is 
placed on the reflected margin over the beaks, and the other 
intermediate, between the umbones and the posterior side; mus- 
cular impression with a large sinus in its narrower part, the im- 
pression being somewhat expanded near to the sinus. 
Section I—Valves divided by a longitudinal groove. 
1. Puouas crispata, pl. XLVIII, f. 1, 2, 3, 4, 5. 
Pholas crispata, First Ed., pl. 9, f. 1, 2, 3, 4,5; Montagu, 
p- 23; Donovan, II, pl. 62; Ib., Pholas parvus, young shell, 
pl. 69; Turton, Biv., p. 63; Fleming, p. 456; Forbes, p. 57. 
Shell strong, inflated, transversely suboyal, very open at both 
sides; one side rounded; the anterior one acutely beaked, at 
which side the superior margins, from the umbonal region to 
the extremity, are thickened, smooth, and reflected, with a 
hollow behind; from the internal end of such reflection ema- 
nates a longitudinal, rather deep furrow,—varying in width in 
different individuals,—and terminating on the basal margin; 
posterior side nearly plain, with irregular, transverse, slight 
wrinkles; anterior side with numerous, thin, undulating, con- 
centric wrinkles, and longitudinal, divergent grooves, producing 
MOLLUSCA. 
[ PHoLaparia. 
a reticulated appearance; inside smooth, white, and glossy, with 
an elevated, longitudinal ridge, corresponding to the external 
furrow; below the umbonal region in both valves is a long, 
flat, greatly curved, transverse tooth; external surface of a dull, 
opaque yellowish-white, sometimes of a ferruginous hue. 
Found on many of the British and Irish coasts, burrowing in 
limestone or clay, its retreat being marked by a circular hole on 
the surface. 
2. Puoxas papyracka, pl. XLIX, f. 4, 6, 7, 9. 
Pholas papyracea, First Ed., pl. 8, f. 4, 6, 7, 9; Goodall, 
MSS.; Turton, Biv., p. 2, pl. 1, f. 1, 2, 3, 4; Pholas lamellata, 
Fleming, p. 456; Pholadidea Loscombiana, Fleming, Conch. 
Dict., p. 147. 
Shell semiclavate ; anterior side yentricose, and very obtuse, 
somewhat rounded, and closed when the valves are shut, 
and quite smooth for about half of its surface; open and 
truncate at the posterior and smaller side, which is provided 
with a produced accessorial ring, of a brownish papyraceous 
appearance, and extending about three-eighths of an inch 
beyond the truncated termination, its diameter increasing out- 
wardly; the hinder half covered with close-set, slightly oblique, 
crenate ribs; near the centre of each valve is a somewhat 
oblique, longitudinal groove, beyond which they are covered 
with coarser and more parallel strie; inside dull white, with a 
longitudinal rib corresponding with the external groove; teeth 
rather short, and compressed ; on the margin above there is an 
erect, slightly triangular, somewhat concave plate, much larger 
in one valve, and containing a portion of the animal fold, but 
destitute of a permanent ligament. Length three-quarters of 
an inch; breadth eleven inches and three-quarters, including 
the annular appendage. 
This ring is divisable into two equal and similar parts, the 
segments being united by a thin elastic membrane; the back 
is provided with two accessorial appendages, with the margins 
of the valves reflected at their anterior side, so as to form a 
double obtuse keel, reaching as far as the longitudinal groove, 
near the end of which is a kind of elevated joint, where the 
accessorial valves are attached. 
3. Puoras LAMELLATA, pl. XLIX, f. 10, 11. 
Pholas lamellata, Turton, Biv., p. 4, pl. 1, f. 5, 6. 
Shell very open anteriorly, where the valves are depressed, 
slightly reflected, and produced into a beaked termination, the 
margins of both valves on this side being strongly serrated, and 
nearly closed posteriorly; with an erect, laminar process on the 
superior margin, over the umbonal region; valves with a nearly 
central, longitudinal groove, emanating from the umbones, and 
terminating on the base; whole surface covered with close-set, 
somewhat obliquely transverse, crenate ribs, which become 
coarser and straighter beyond the longitudinal groove; inside 
white, and smooth, with a longitudinal rib in the middle, cor- 
responding to the external groove; teeth long, compressed, and 
slender, with a triangular process above them; destitute of 
accessorial valves. 
This species is nearly allied to, if not a variety of the pre- 
ceding shell. It was introduced by Dr. Turton, who remarks, 
“Tt has been suggested to us, that a belief is entertained of 
this being the young of P. papyracea. But as we have oppor- 
tunities of examining each of them in every stage of their 
growth, both perfect and with the valves separated, we can with 
