Pecten. 
MOLLUSCA. BIVALVIA. 
385 
380. P. Puslo. — Shell oblong oval equivalve, with forty 
rounded and nearly smooth strise, which are alternately smal- 
ler.” 
P. parvus, List. Conch, t. clxxxix — Ostrea Pusio, Linn. Syst. i. 1146. — 
Pecten Pusio, Turt. Biv. Brit. 215. t. xvii. f. 2 — From the rocks in 
Torbay. 
Shell |ths of an inch long, and i an inch broad ; brownish-white, with 
chocolate transverse zigzag bands, often saffron or crimson, but variable in 
colours ; the under valve usually clear white ; with about 40 fine rounded 
striae, which are mostly alternately larger and smaller, and very slightly mu- 
ricate about the margin.” — Turton. 
381. P. Islandicus.--R\hs numerous, rough, unequal, irregu- 
larly grouped. 
ZrW'^. Conch, t. Mlvii. f. 4. Turt. Conch. Diet. 258. Biv. Brit. 21G. — 
West coast of Scotland. 
Length upwards of 3 inches; colour reddish; ribs from 70 to 100, with 
rough scales, the ribs are grouped in pairs or otherwise ; the furrows are re- 
ticulated. A specimen in my possession, from the silt of the Clyde, given 
me several years ago by Mr Laskey, is inches in length, and 3 inches in 
breadth. 
382. P. ohsoletus .—Sm'fsice oi the shell delicately shagreened. 
Penn. Brit. .Zool. iv. 102. t. Ixi. f. 66. Don. Brit. Shells, t. i. f. 2. Mont. 
Test. Brit. 149. Sup. 57 — Ostrea laevis, Maton and Rackett., Linn. 
Trans, viii. 100. t. iii. f. 5 — P. oh. Turt. Biv. Brit. 213. t. ix. f. 6. — In 
sandy bays. 
Shell rarely exceeding an inch in diameter ; colour purple, or mottled with 
brown ; surface sometimes even, with obsolete ridges, or with the margin re- 
gularly ribbed; but in all cases the reticulated surface, when seen by a lens, 
is a sufficiently distinguishing mark of this, otherwise, variable species. 
383. P. Imms . — Smooth and glossy, with unequal striated 
ears. 
Penn. Brit. Zool. iv. 102. Mont. Test. Brit. Sup. 61. Turt. Biv. Brit. 
212 Western coasts of England. 
Diameter about half an inch ; colour white ; slightly and irregularl y wrink- 
led concentrically ; thin, and semitransparent. 
384 P. similis . — Shell thin, semitransparent, smooth, beau- 
tifully clouded with brown, of a compressed globose form, with 
unequal ears. 
Laskey., Wern. Mem. i. 387* t. viii f. 8.— Found in the Frith of Forth. 
The under side of the shell is more prominent than the upper. The P. iu- 
midus is probably only a variety of this species. 
EXTINCT SPECIES. 
1. P. Triangular, nearly even, front semicircular, margin 
notched ; convex valve ribbed, larger costce six, three smaller between each ; 
posterior auricle large. — Sower. Min. Conch, t. Ivi. f. 1, 2. — In Green Sand. 
2. P. quinquecostata. — Subtriangular, rather oblique, front semicircular, 
VOL. I. B b 
