112 lAI.IKiMtNU ACADEMY OF SCIENCES. 



Genus Protocardia llci/rich. 



SlicU (ilobosc, willi a posterior area sharply tlisliiij^uislicd by sculpture Iroin the rest ol the 

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



TyiH', Carili)i)i} hillnnnm (Sowcrhy). 



76. Protocardia centifilosa ('tirpenter. 



Cardiuin var. cnitijilosinn Ci-K., Brit. Assn. Rept. 1863, ]). 642. 



Cardmm centiftlosum Cpr., Garb, Pal. Cal., \'o\. II, p. 99, 1869. Cooper, 7th Ann. Rept. Cal. St. 



Min., iSSS, p. 232. Wii.i.iAMSdN, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 189. 

 Protocardia centifilosa Cpr., Dall, Trans. Waijner Inst. Sci., Vol. Ill, Part 5, 1900, p. 1113. 



Shell small, suboval, ventricosc, thin; umbones central, prominent, only very slijjhtly bent; 

 surface sculptured by numerous fine, close-set, rounded, radiatint; 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.; all. 22.5 mm.; diam. 15 mm.. 



Di.slingiii.slial)li' hy (ho nearly circular oulliiio and ninnerous fine, radiating 

 ridges. Specimens identified by Dr. Dall. 



Not nnconiinon in the Pliocene of Deadmaii Island and Timm'.s Point; rare in 

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

 liath-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 Die^o wcdl (Dall): Santa Barbara 

 (Arnold). 



Pliocene. — Snnol, Alameda County (Cooper). 



Superfamily VENERACEA. 



Family XXVII. VENKRID/E. 



Subfamily VENERlNyE. 



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 impre.ssion with a short 

 oblique or sometimes horizontal sinus. 



Cytherea is a characteristic species. 



