ARNOLD — THE PALEONTOLOGY AND STUATIGKAPHY OF SAN PEDRO. 141 



74. Cardium (Lasvicardium) datum Somcrbjj. 



Platk. XX. 



Cardtum e/a/ian Sny., Conch 111., Vol. I, 1838. Reeve, Conch. Icon., PI. YIII, fig. 4r. Valen- 

 ciennes, Voy. Venus, PI. XVII, fig. i, 1846. 



Liocardium elalum Sby., Carpenter, Brit. Assn. Rept., 1863, p. 642. Cooper, ytli Ann. Rept. Cal. 

 St. Min., 1888, p. 246. Keep, West Coast Shells, p. iSi, 1892. Williamson, Proc. 

 U. S. Nat. Mus., Vol. XV, 1892, p. 190. 



LcEvicardium datum Sby., Gabb, Pal. Cal., Vol. II, ]). 99, 1869. Dall, Trans. Wagner Inst. 

 Sci., Vol. Ill, Parts, iQOo, p. 11 11. 



Shell large, oval, obliciue, elongated, eqiiivalve, somewhat inequilateral; surface scul|)tured 

 by numerous faint, squarish, radiating ribs, and fine, wavy incremental lines; inner surface of margin 

 corrugated ; hinge strong, with one prominent cardinal and one prominent anterior lateral tooth in 

 each valve ; muscle-impressions distinct. 



Dimenstotis. — Long. 144 mm.; alt. 167 mm.; diam. 136 mm. 



This is tlic largest of the Cnrdiuhc, and is easily recognizable by its immense 

 size aiul nearly smooth snrface. A line pair of this species, described above, and 

 ligiired, was found in the upper San Pedro series at the north end of the San Pedro 

 bhif!. Another specimen was obtained by Dr. A. A. Wriglit and Mrs. Oldroyd in 

 the upper San Pedro deposits of Los Cerritos. This species is one of the typical 

 soiillicrn forms found in the upper San Pedro series. 



Living. — San Pedro to Mazatlan (Gooj)er). 



Pkii^tocerte. — San Pedro (Cooper; Arnold): San Diego (Gabb; Dall). 



75. Cardium (Laevicardium) substriatum Cunnnl. 



Cardium substriatum CoN., Jour. Phil. Acad. Sci , Vol. VII, 1S37, p. 228, PI. XVII, fig. 2. 

 Liocardium substriatum Qo'a , ^ crueritatum Gould, (^fide Carpenter, Brit. Assn. Rept., 1863, 



p. 642.) Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 246. Keep, West Coast 



Shells, p. 181, fig. 154, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, 



p. 190. 

 L(Evicardium substiiatum Coti., Gabb, Pal. Cal., Vol. II, p. 99, 1869. Dall, Trans. Wagner Inst. 



Sci., Vol. Ill, Part 5, 1900, page nil. 



Shell small, obliquely ovate, ventricose, thin ; surface smooth, except for minute incre- 

 mental lines and nearly obsolete radiating stride ; one small sharp cardinal tooth in each vahe ; two 

 narrow elongated lateral teeth in each valve, the posterior one in the left valve not i)rominent ; 

 interior of margin finely crenulated. 



Dimensions. — Long. 17 mm.; alt. iS mm.; diam. 13 mm. 



Distinguishable l)y its small size and smooth surface. Specimens identified 

 by Dr. Dall. 



Kare in the lower San Pedro series of Doadman Island and San Pedro, and 

 in the upper San Pedro series of Deadman Island, San Pedro, Crawfish George's, 

 and Los Cerritos. Found also in the Pleistocene at Twenty-sixth Street, San Diego. 



Living. — Monterey to South America (Cooper). 



Pleistocene. — Santa Barbara; San Pedro; San Diego (Cooper): San Pedro 

 (Arnold): San Diego (Arnold). 



