Pectex. MOLLUSC A. BIVALVIA. 385 



380. P. Push. — " Shell oblong oval equivalve, with forty 

 rounded and nearly smooth stria?, 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 gths of an inch long, and 4 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. — Ribs numerous, rough, unequal, irregu- 

 larly grouped. 



List. Conch, t. wlvii. f. 4. Turt. Conch. Diet. 258. Biv. Brit. 21C — 

 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 3i inches in length, and 3 inches in 

 breadth. 



— 382. P. obsoletus. — Surface of the shell delicately shagreened, 



Perm. Brit. Zool. iv. 102. t. lxi. f. 66. Don. Brit. Shells, t. i. f. 2. Mont. 

 Test. Brit. 149. Sup. 57 — Ostrea hevis, Maton and Baekett, Linn. 

 Trans, viii. 100. t. iii. f. 5 — P. ob. 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. IcEvis. — 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 irregularly 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. hi. 

 midus is probably only a variety of this species. 



EXTIXCT SPECIES. 



1. P. quadricostata. — Triangular, nearly even, front semicircular, margin 

 notched ; convex valve ribbed, larger costse six, three smaller between each ; 

 posterior auricle large.— So veer. Min. Conch, t. lvi. f. 1, 2 — In Green Sand. 



2. P. quinquecostata. — Subtriangular, rather oblique, front semicircular, 

 VOL. I. B b 



