l^HOLAS. 
MOLLUSCA. PHOLADtE. 
45T 
555. P. tuber ciilatus. — Shell open at the anterior end, with a 
rough tubercle on the margin above the teeth, and a single 
oval calcareous plate at the hinge extending to the anteal ex- 
tremity. 
TurL Biv. Brit. v. t. i. f. 7? 8 — Torbay. 
Length three-quarters of an inch, breadth an inch and a half; white ; front 
of the shell slightly elongated into a beak ; anterior compartment with rough 
ribs, which gradually disappear towards the retral truncated extremity. 
556. P. conoides. — Transversely elongated, anteal division 
short, tumid, rounded, the retral division produced and subcom- 
pressed. 
Parsons^ Phil. Trans. 1765, i. t. 1. — P. striatus, Z-inn. Syst. i. 1111.— » 
P. nanus, Pult. Dorset. 27* — P. stri. Don. Brit. Shells, t. cxvii. Mont 
Test. Brit. 26. Turt. Biv. Brit. 11 — In ship planks. 
Length half an inch, breadth an inch ; ridges in the anteal compartment 
crowded, rough ; in the retral wider and smoother, well marked along the 
furrow ; nearly closed retrally ; when young, Very open anteally, and beaked, 
but filling up with smoother shell (like P. papyracea) towards maturity ; one 
large rounded accessory plate over the hinge, behind which is a lengthened 
one, and a third connecting the ventral margins of the shells ; a long slender 
curved tooth in each valve. 
The valves not divided by a groove. 
557. P. djactylus. — Conically transverse, with concentric, 
waved, muricated ridges, having longitudinaJ grooves, most con- 
spicuous anteally ; margin above the beaks reflected, circular, 
with four accessory plates. 
P. striatus, 'List. Conch, t. ccccxxxiii. Anat. t. xix. f. 1 , 2 — P. dact. 
Lmw. Syst. i. 1110. Borl. Corn. 278. t. xxviii.-xxxi. Mont. Test. 
Brit. 20. Twt. Biv. Brit. 8.— In rocks and submarine trees. 
Length sometimes 2 inches, and breadth 7 ; wide and open before ; slight- 
ly compressed behind ; shell in front of the hinge produced into a kind of 
beak, with the edge thin and reflected. 
558. P. parvus. — Shell open, and produced into a beak an- 
teally, with a smooth tubercle on the margin above the teeth, 
and a single accessorial valve at the hinge. 
Mont. Test. Brit. 22. t. i. f. 7? 8. Turt. Biv. Brit. 9 — Submarine wood 
on the south coast of England. 
Length fths, breadth 1| inches ; transversely striated, with longitudinal 
ridges anteally ; the anteal opening is oval, and the fold above the beaks des- 
titute of cells. Montagu is inclined to consider this shell as the P. parvus of 
Pennant, (Brit. Zool. iv. 77* t. xl. f. 13.) though it is not improbable that it 
is related to the young of P. papyracea. 
559- P. Candidas. — Shell nearly closed anteally; a tooth- 
like process on the hinge ascending obliquely and retrally ; 
margin above the hinge reflected, and covered with an elongated 
accessorial^late. 
Concha Candida, List. An. Aiig. 193. t. v. f. 39, Conch, t. ccccxxxv.— P. 
