112 MAZATI-AN BIVALVES 



excurved ; ligamental pit in the umbo. One minute valve. 

 ('02 across,) and one ? adult were found. Long. '06, lot. '08, 

 alt. -04. 



Sah. — Mazatlan ; 2 valves off Spondylus ; JJpool Col. 



Tablet 500 contains tke larger valve. 



Genus PYTHINA, Hinds. 



Voy. Sulph. 1844, p. 70. — Known by its very trigonal shape, 

 often ventrally indented and divaricately sculptured. It 

 must not be confounded with Pjthia, (Sc/<?/7h. 1817, = Scara- 

 bus, Monff'. : nor with Pythia, Gray, 1821,= Conovulus 

 myosotis, &c. 



= Kellia, pars. Phil. Sanclh. Conch, p. 344 : — Wbodic. Man. 

 Moll. ii. 295. 



160. PtTHINA STJBLiEVIS, n. s. 



F. t. minimd, alba, epidermide tenuissima stramined indutd ; 

 valde incequilatetali, transversa, trigona, vmhonibus promineyi- 

 tibus, margine ventrali sen recto seu suhiriciirvafo ; leein. seu 

 striulis exillimis divaricate radiantibus ; dentibus card, altera 

 valvd ii. divergentibus, quarum una major, alterd nvllis ; dent, 

 lat. elongatis, exillimis. 



Two j)airs and two valves of this shell were found, differing 

 in outline and scidpture, but probably identical. The character 

 of the hinge seems more related to Montacuta than to Kellia. 

 The smallest valve is '025 across : the largest measm*es 

 long. -05, lat. '08, alt. -025. 



Sab. — Mazatlan : on Chama and Spondylus, extremely rare ; 



Jj'pool Col. 



Tablet 501 contains the two pairs, one closed, the other 

 opened. 



Gentts MO]?fTACUTA, Turt. 



Conch. Dithyr. Brit. p. 58, 1822. 



According to Clarl; Moll. Test. Mar. Br. pp. 88, 94, the 

 typical species of this genus belong to the Anatinidre, while 

 the aberrant species remains to constitute a new familv. Of 



