112 MAZATLAN BIVALVES 
excurved ; ligamental pit in the umbo. One minute valve, 
(02 acrcss,) and one Padult were found. Long. ‘06, lat. 08. 
alt. *O4. 
Hab.—Mazatlan ; 2 valves off Spondylus; Z’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, Gray, 1821,= Conovulus 
myosotis, &c. 
=Kellia, pars, Phil. Handb. Conch. p. 344:—Woodw. Man. 
Moil. 11. 295. 
160. PYTHINA SUBLEVIS, 2. Ss. 
P. t. minima, albé, epidermide tenuissimd stramined induté ; 
valde inaquilaterali, transversa, trigond, umbonibus prominen- 
tibus, margine venirali seu recto seu subincurvato; levi, seu 
striulis exillimis divaricate radiantibus ; dentibus card. altera& 
valvé i. divergentibus, quarun una major, altera nullis ; dent. 
’ lat. 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. 
Hab.—Mazatian ; on Chama and Spondylus, extremely rare ; 
E’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 Anatinide, while 
the aberrant species remains to constitute a new family. Of 
