110 MAZATLAN BIVALVES 



Compare Chironia Laperousii, Desk, in Woodw. Man. Moll. 



pt. 2. p. 295, pi. 19, f. 11. 



One fine fresh valve was found of this species, which is not 

 unlike Bornia luticola, Vol. 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. 

 Long. '16, lat. '2, alt. 'I. 

 Hah. Mazatlan ; 1 valve off Chama ; L'pool Col. 



Tablet 497 contains the specimen. 



GENUS LEPTON, Turt. 



Turton, Conch. Dytli. 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 Arcadse 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 Kelliadse, and Woodward 

 unites the whole tribe to the Lucinidae. 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, n. s. 



L. t. papyracea, alba, concentrice undulatd, punctulis mini- 

 mis creberrimis confertd ; incequilaterali, subquadratd, 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 dementia, 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- 



