TRIBE PHOLADARIA. Q 
trically striated: dorsal edge posteriorly reflected and inflated : 
with two anterior, dorsal, sub-ovate, accessory valves ; the epidermis 
anteriorly running down upon two flattened valves and then a cal- 
careous tube conspicuous at the extremity. ,%,..1,3,.—W. Colwm- 
bia. Very like Papyracea: the intermediate ages without the tube. 
P. Paryracea.* Turt. B. p. 2. t.1.f. 1 to 4.—Sow. G.— 
Reeve. t. 24. f.3.—W. 8. t. 1. f. 1. Ovate oblong, closed and 
very obtuse posteriorly, open and truncated anteriorly, posterior mar- 
gin reflected at the hinge into a thin nearly erect narrow plate ; 
dirty white, divided by a longitudinal groove; anteriorly with de- 
pressed concentrical lamellze, posteriorly towards the hinge with close 
obliquely curved toothed thin ridges, the remaining portion nearly 
smooth : nacreous white within.— Young. (P. Lametuata. Turt. 
Biv. t. 1. f. 5, 6—W. S. t. 1. f. 2.)—Without the smooth space 
at the posterior ventral edge, and consequently with a large oval 
gape. 13.—England. 
P. Curta. Sow. Z. P. 1834. Oval, anteriorly acuminated, 
posteriorly rounded : valves divided by a transversely grooved band ; 
the posterior area obliquely divided, the dorsal portion with radia- 
ting wrinkles and transverse strize, the ventral thinner and sub- 
inflated : anterior surface with concentric strize: accessory valve 
solitary, posterior dorsal, sub-acuminated at the ends and con- 
tracted in the middle: upper and lower edges with a horny testa- 
ceous epidermis which on the dorsal surface is anteriorly forked. 
7542 —W. Columbia. 
P. Cornea. Sow. Z. P. 1834. Oblong, thin, posteriorly 
rounded, anteriorly obtuse: a thin horny epidermis ; valves divided 
by a band; posterior area obliquely divided, the dorsal portion 
being rather rugose, the ventral smooth: anterior surface larger 
and smooth ; with three accessory valves, the posterior dorsal one 
rounded, and sub-emarginated anteriorly : anterior gape large. 3,,°. 
—W. Columbia. 
PVonerneunara.®,. Lurt, Bp. Seto La f. 75.8:—W..S., t. 
1. f. 3. Oblong with the ventral margin posteriorly sinuated, but 
not forming a beak at its extremity; gape nearly orbicular: the 
transverse rough strie disappearing anteriorly after crossing the 
longitudinal groove : a single accessorial valve and a rough tubercle 
on the edge above the teeth. $..13.— England. 

1Tn this genus we must include Turton’s 
XYLOPHAGA. 
Orbicular, equivalve, inequilateral, posteriorly gaping, with two 
sub-triangular testaceous accessory pieces, a minute cardinal 
