Pectex. mollusc a. EIVALVL\. 385 



380. P. Pu-iio. — " Shell oblong oral cquivalve, with forty- 

 rounded and nearly smooth striae, which arc alternately smal- 

 ler;' 



P. parvus, List. Conch, t. clxxxix — Ostrea Piisio, Linn. Syst. i. 1140.— 

 Pecten Pusio, Tnrt. Biv. Brit. 215. t. xvii. tl 2 — From the rocks in 

 Torbay. 



'• Shell |ths of an inch long, and }, an inch broad ; brovvnish-wliite, vvith 

 chocolate transverse zigzag bands, often saffron or crimson, but variable in 

 colours; the under valve usually clear white; with about 40 fine rounded 

 striie, which are mostly alternately larger and smaller, and very slightly mu- 

 ricate about the margin." — Turton. 



38L p. Idandicus. — Ribs nmncrous, roiigl), unequal, irregu- 

 larly grouped. 



List. Conch, t. ailvii. f. 4. Turt. Conch. Diet. 258. Biv. Brit. 216— 

 AVest 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 tlite silt of the Clyde, given 

 me several years ago by Mr I-askey, is 3,^ inches in length, and 3 inches in 

 breadth. 



382. P. ohsoletus. — Surface of the shell delicately shagreened. 



Penn. Brit. Zool. iv. 102. t. Ixi. f. GC. Don. Brit. Shells, t. i. f. 2. Monf. 

 Test. Brit. 149. Sup. 57 — Ostrea la;vis, Malon and Rackett., Linn. 

 Trans, viii. 100. t. iii. f. 5 — P. ob. Turt. Biv. Brit. 213. t. ix. f C— 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, otiierwise, variable species. 



383. P. Icev'is. — Smooth and glossy, with unequal striated 



ears. 



/»e»m. Brit. Zool. iv. 102. Mont. Test. Brit. Sup. (il. 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. tu- 

 midux is probably only a variety of this species. 



EXTINCT SPECIES. 



1. p. quadricostala. — Triangular, nearly even, front semicii cular, margin 

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

 posterior artricle large. — Soiver. Min. Conch, t. Ivi. f. 1, 2 — In Green Sand. 



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

 VOL. I. B b 



