1-10 CALIFUUNIA ACAUKMY OF 8CIKNCE8. 



collection of Delos Arnold. Found nhiindiuilly in tlic I'loistocene nf Twonty-sixtli 

 Street and Spanish Hij^ht, San Diego. 



Jjiriny. — (inlf of California to Panama (Dall). 



Pk'ixtdccnr. — San I'cdrn (( 'ii<)|irr; Arnold) : San l)i('i!;o (T'oopor; l)all; Anidld). 



Subgenus Cerastoderma Mm-ck. 



Shell rotund or obovatc, closed; witli strong ribs obsoletely granulose or intricate or smooth; 

 no posterior or anterior area; channels single; hiiige noiin:il. 



Type, Cardium ednle (Linm'). 



73. Cardium (Cerastoderma) corbis Marlyn. ^ 



Pectunculis corbis Mart., Univ. Conch., PI. XXVIII, fig. 2, p. 17S4. 



Cardittm corbis Mart., Carpenter, Rrit. Assn. Rept., 1863, p. 642, -=C. califoruicum Con. =C. 



7iuflal/i Coti. {/ide Garb, Pal. Cal, Vol. II. p. 98, 1869). Cooper, 7lh Ann. Rept. Cal. 



St. Min., 1888, p. 232. Keep, West Coast Shells, p. 180, fig. 153, 1892. Dai.i,, Tmns. 



Wagner Inst. Sci., Vol. Ill, Part 5, 1900, p. 1093. 



Shell large, subtrigonal, ventricoft, thick; umbones prominent, anterior to center; surlace 

 ornamented with about thirty-seven prominent, regular, squarish, close-set, radiating ridges, which are 

 made more or less rugose bj' incremental ridges on their surface; near the posterior margin these 

 ridges become more rounded and less prominent; between the ridges are equal, deep, canal-like grooves; 

 margin crenulated; ligament short, e.xternal, prominent; each valve with one prominent cardinal 

 tooth, and two laterals, one anterior and the other posterior; muscle impressions prominent, subequal. 



Dimensions.- — Long. 71 mm.; alt. 71 mm.; diam. 57 mm. 



Distin.irnislialilo by the regular, only slightly rugose ridges. Specimens 

 identified by Dr. Dall. 



Found in iIil' lnwcr San IVdro series of Deadman Island and San Fedro; and 

 in the n])per San Pedro series of Deadman Island, San Pedro, LosCerritosand Crawfi-sh 

 George's. Found also in the Pleistocene of the hath-house, Santa Barbara. 



Living. — Kodiak to Santa Barbara; Kamtschatka (Cooper). 



Pleistocene. — San Francisco; ^ronlcrcy; San Pedro (Cooper): San Pedro; 

 Santa Barbara (Arnold). 



Subgenus Laevicardium Svjainson. 



Shell thin, oval, closed ; middle of the valves smooth or feebly radially sculptured ; ends 

 with a smooth area; hinge normal, but with the anterior laterals springing from the umbonal cavity; 

 periostracum smooth. 



Type, Cardium norvegicum (Spengler). 



