142 CALIFQENIA 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 hillanum (Sowerby). 



76. Protocardia centifilosa Carpenter. 



Cardium var. centifilosum Cpr., Brit. Assn. Rept. 1863, p. 642. 



Cardium ceniifilosum Cpr., Gabb, Pal. Cal., Vol. II, p. 99, 1869. Cooper, 7th Ann. Rept. Cal. 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. 1113. 



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. 



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



Distinguishable by the nearly circular outline and numerous fine, radiating 

 ridges. Specimens identified by Dr. Dall. 



Not uncommon in the Pliocene of Deadman Island and Timra'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 Count}' (Cooper). 



Superfamily VENERACEA. 



Family XXVII. VENERID^. 



Subfamily VENER, IN A!. 



Genus Tivela Link. 



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 sliort 

 oblique or sometimes horizontal sinus. 



Cytherea is a characteristic species. 



