PECTEN.— Plate XXI. 



C[uam longd, crassiusculd, compressa, 

 riter siabrd, concentrice undato-Uneatd, aqnilatei-ali, 

 subaquivalvi, valvd dextrd convexiore, valvis costis sul- 

 cata diiodecwi fortUer radiatis ; flavicante, valvd si- 

 nisti'd rufo-nigro maculatd. 

 The geater Pecten. Shell somewhat triangularly 

 ovate, higher than long, rather thick, compressed, 

 peculiarly rough thi'oughout, concentrically wave- 

 lined, equilateral, nearly equivalve, right valve the 



more convex, valves strongly rayed with twelve 

 grooved ribs ; yellowish, left valve spotted with red- 

 black. 



Ostrea radula, Linnaeus, Syst. Nat. p. 1145. 

 Odrea maculosa ? Gmelin. 



Ilab. Philippine Islands ; Cuming. 



The left valve of this weU-known species is peculiarly 

 compressed at the umbo. 



