180 CALIFORNIA- ACADEMY OF SCIENCES. 



132. Cryptomya calif ornica Conrad. 



Sphcenia californica Con., Journ. Phil. Acad. Nat. Sci., Vol. VII, 1837, p. 234, PI. X\'II, fig. it. 



Cpr., Proc. Zool. Soc, 1856, p. 210. 

 Cryptomya californica CoN., Proc. Phil. Acad. Nat. Sci., 1849, p. 121. Cpr., Brit. Assn. Rept., 1863, 



p. 637, =C. oralis Qos. {Jide Gabb, Pal. Cal. Vol. II, p. 90, 1869). Cooper, 7th 



Ann. Rept. Cal. St. Min., 1888, p. 237. Keep, West Coast Shells, p. 205, 1892. 



Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 183. Dall, Trans. Wagner 



Inst. Sci., Vol. Ill, Part. 4, 1898, p. 859. 



Shell rather small, subelliptical, convex, equivalve, subequilateral, thin; anterior e.\tremity 

 biangular, with faint fold running down from umbo to lower portion of this e.xtremity; posterior 

 e-xtremity evenly rounded, slightly more produced below middle; ventral margin slightly arcuate; 

 surface sculptured by numerous fine, concentric, incremental lines; right valve with prominent 

 lamellar tooth, in which is a shallow cartilage-pit or chondrophore; left valve with a broad fosset; 

 pallial sinus obsolete. 



Dimensions. — Long. 26.5 mm.; alt. iS mm.; diam. 5 mm. 



Distinguishable from young of Tresus nuttalli by the lamelhir elevated tootli 

 and obsolete sinus. Specimens identified by Dr. Dall. 



Found in the lower San Pedro series at Deadman Island and San Pedro; 

 and in the upper San Pedro series at San Pedro, Deadman Island, Los Cerritos, 

 Crawfish George's, and Long Beach. Found also in the Pleistocene at Twenty-sixth 

 Street and Spanish Bight, San Diego; and at the old irrigating ditch and Barlow's 

 ranch, Ventura. 



Living. — British Columbia to Lower California (Dall). 



Pleistocene. — San Pedro (Arnold): San Diego well (Cooper): San Diego; 

 Ventura (Arnold), 



Pliocene. — Santa Rosa; Twelve Mile House, San Mateo County; Soquel, Santa 

 Cruz County; San Fernando; San Diego well (Cooper). 



Miocene. — Siebeck's, Santa Clara County; Griswold's, San Benito County; 

 Foxin's, Santa Barbara County (Cooper). 



Family XXXVH. CORBULID.F. 

 Genus Corbula (Bruguiere) Lamarck. 



Valves unequal, the right usually larger, both more or less rostrate; hinge with (in the right 

 valve) a single large tooth below the beak, with a deep resiliary pit behind it, and no lateral laminae; 

 the left valve without laterals, with a process upon which the resilium and ligament are inserted, in 

 front of a socket, into which the cardinal tooth of the right valve fits; beaks prominent; sculpture 

 variable, never strongly radial; pallial line with a small sinus or none; kuuile and escutcheon usually 

 absent; ligament chiefly internal. 



Corhula galli"n Lam. is a characteristic species. 



