112 MAZATLAN BIVALVES 



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

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

 alt. '04. 



Hob. Mazatlan ; 2 valves off Sppndylus ; L'pool Col. 

 Tablet 500 contains the 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 Pythia, Schum. 1817, = Scara- 

 bus, Montf. : nor with Pythia, G-ray, 1821,= Conovulus 

 myosotis, &c. 



= Kellia, pars, Phil. Handb. Conch, p. 344 : Woodw. Man. 

 Moll. ii. 295. 



160. PYTHINA SUBL^VIS, n. s. 



P. t. minima, alba, epidermide tenuissimd stramined indutd ; 

 valde inaequilaterali, transversd, trigond, umbonibus prominen- 

 tibus, margine ventrali seu recto seu siibincurvato ; Icevi, seu 

 striulis exillimis divaricate radiantibus ; dentibus card, alterd 

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

 lot. elongatis, exillimis. 



Two pairs and two valves of this shell were found, differing 

 in outline and sculpture, but probably identical. The character 

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

 The smallest valve is '025 across : the largest measures 

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

 Hob. Mazatlan ; on Chama and Spondylus, extremely rare ; 



L'pool Col. 



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

 opened. 



GENUS MONTACUTA, Turt. 



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



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

 typical species of this genus belong to the Anatinidse, while 

 the aberrant species remains to constitute a new family. Of 



