142 CALIFORNIA ACADEMY OF SCIENCES. 



Genus Protocardia Beyrich. 



Shell globose, with a posterior area sharply distinguished by sculpture from the rest of the 

 surface; closed; hinge normal; no lunule or escutcheon. 



Type, Cardium hillaniim (Sowerby). 



76. Protocardia centifilosa Carpenter. 



Cardiiim var. centifilosmn Cpr., Brit. Assn. Rept. 1863, p. 642. 



Cardium ccntifilosian Cpr., Gabb, Pal. Cal., Vol. II, p. 99, 1869. Cooper, yth Ann. Rept. Cat. St. 



Min., 1888, p. 232. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 189. 

 Protocardia centifilosa CpR., Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 5, 1900, p. 11 13. 



Shell small, suboval, ventricose, thin; umbones central, prominent, only very slightly bent; 

 surface sculptured by numerous fine, close-set, rounded, radiating ridges, which are made slightly 

 rugose by numerous fine, incremental lines on their surface; thin, sharp teeth in each valve; pallial 

 sinus shallow, wide; margin beautifully and sharply serrate. 



Ditnensiotis . — Long. 23 mm.; alt. 22.5 mm.; diam. 15 mm.. 



Distinguishable by tlie nearly circular outline and numerous fine, radiating 

 ridges. Specimens identified by Dr. Dall. 



Not uncommon in the Pliocene of Deadman Island and Timm's Point; rare in 

 the lower San Pedro .series of Deadman Island. Found also in the Pleistocene at 

 bath-house and the Pliocene of Packard's Hill, Santa Barbara. 



Living. — Monterey to Catalina Island (Cooper). 



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



Pliocene. — San Pedro (Arnold): San Diego well (Dall): Santa Barbara 

 (Arnold). 



Pliocene. — Sunol, Alameda County (Cooper). 



Superfamily VENERACEA. 



Family XXVIT. VENERID^. 



Subfamily VENERIN^. 



Genus Tivela Linl-. 



Shell triangular, subequilateral, cuneiform; three to five cardinal teeth in one valve, four to 

 six in the other; anterior lateral tooth narrow, elongated, compressed; pallial impression with a short 

 oblique or sometimes horizontal sinus. 



Cyfherea is a characteristic species. 



