110 MAZATLAN BIVALVES 
_ Compare Chironia Laperousii, Desh. in Woodw. Man. Moll. 
pt. 2. p. 295, pl. 19, f. 11. 
One fine fresh valve was found of this species, which is not 
unlike Bornia luticola, Val. in Rec. Obs. Humb. The latter 
however appears to have very irregular ridges of growth and 
stronger teeth. The shell is distinguished by its transverse 
shape, rough, somewhat pilose epidermis, and minute teeth. 
It seems to partake of the characters of Lasea and Kellia. 
ong AGs tat. 2. ale. 2 V. 
Hab.—Mazatlan ; 1 valve off Chama; Z’pool Col. 
Tablet 497 contains the specimen. 
Genus LEPTON, Turt. 
Turton, Conch. Dyth. Brit., 1822, p.61.—The typical species 
of this genus are easily distinguished by their flat, shagreened 
valves, and diverging, prominent teeth. They are ranked 
with Arcade by Clark, Moll. Test. Mar. Brit. p.'75 et seq. 
Dr. Gray constitutes for them a fresh family : while Philippi 
follows Forbes in locating them with Kelliade, and Woodward 
unites the whole tribe to the Lucinide. Much more must be 
learned of the animals of the foreign species before their true 
position can be ascertained. Some of the species can with 
difficulty be separated from Kellia by the shell alone. 
157. Lepton CLEMENTINUM, 2. S. 
L. t. npapyraced, alba, concentrice undulata, punctulis mina- ° 
b) b) t) 
mis creberrimis conferta ; inequilaterali, subquadrata, umboni- 
bus magnis, prominentibus ; marginibus dorsalibus incurvatis ; 
dent. card. uno, celato, fossam ligamenti parvam, depressam 
adjiciente ; dent. lat. duobus curtis, divergentibus. 
Although I had the misfortune to damage the only valve 
found of this beautiful species, yet the characters are so well 
marked that it appears best to describe it. The shell is shaped 
like Clementia, with a few stout, rather distant, concentric un- 
dulations: texture transparent, and exhibiting a most minute 
cellular structure, very evident by transmitted light. Hinge 
very small, with a tiny, sunken, ligament pit and a minute 
almost hidden cardinal tooth adjacent; and two very short 
but distinct diverging laterals. The umbo is made very prom- 
