146 CALIFOENIA ACADEMY OF SCIENCES. 



Subfamily Dosininai. 

 Genus Dosinia Scoiioli. 



Shell orbicular, compressed, concentrically striated, pale, ligament sunk; lunule deep; hinge 

 like Cytherea; margin even; pallial sinus deep, angular, ascending. 



Dosinia discus Reeve is a characteristic species. 



[S. D.] Dosinia ponderosa Gray. 



Artemis poyidcrosa Gray, Analyst, Vol. VIII, 1838, p. 309. 



Dosinia ponderosa Gray, H. & A. Adams, Gen. Rec. Moll., Vol. II, p. 432; =^ Cytherea gigatiica 



Sby. {fide Gabb, Pal. Cal. Vol. II, p. 97, 1869). Cooper, 7th Ann. Rept. Cal. St. 



Min., 1888, p. 239. 



Shell large, thick, equivalve, subcircular in outline, convex; surface sculptured by many 



obsolete, concentric lamellae, and fine, incremental lines; lunule deeply impressed, small, finely 



sculptured; beaks small, not elevated; hinge very wide and heavy, with three heavy, cardinal teeth, 



the posterior one in the right valve being bifid; ligament long, narrow, sunken. 



Dimensions. — Long. 119 mm.; alt. 105 mm.; diam. 55 mm.; lunule 15 mm. 



Common in the uj»per San Pedro series (Pleistocene) of Twenty-sixth Street, 

 San Diego. 



Living—West Mexican coast to Panama (Carpenter). 



Pleistocene. — San Diego (Hemphill; Arnold). 



Pliocene. — Kirker's Pass, Contra Costa County; San Fernando (Cooper): 

 Stanford University, Santa Clara County (Arnold). 



Genus Venus Linne. 



Shell thick, ovate, smooth, sulcated, or cancellated; margins minutely crenulated; cardinal 

 teeth three in each valve; pallial sinus small, angular; ligament prominent; lunule distinct. 



Venus verrucosa Linne is a characteristic species. 



[S. B.] Venus perlaminosa Conrad. 



Mercenaria perlayninosa Con., Proc. Phil. Acad. Sci., 1855, p. 267. Gabb, Pal. Cal.. Vol. II, 

 pp. 22, 55, 94; PI. V, fig. 38; PI. XV, fig. 14; 1869. Cooper, 7th Ann. Rept. Cal. St. 

 Min., 1888, p. 250. 



Venus kennerleyi RvE., Icon. Conch. ( Venus'), PI. XII, fig. 41 {fide Gabb). 



" Shell large, thick, rounded, subquadrate, very inequilateral; beaks anterior; anterior end 

 excavated under the beaks, rounded below; base broadly rounded; posterior end convexly truncated; 

 cardinal margin slightly convex. Surface closely marked by numerous prominent, recurved, 

 lamelliform concentric ribs. Lunule marked by an impressed line, Hinge robust. Pallial line 

 strong, sinus small, oblique, acute at base; muscular scars nearly equal in size; margin minutely 

 crenulated; the purple color between the pallial line and the base is very persistent." — [Gabb.] 



Found in the Pliocene at Packard's Hill, and in the Pleistocene at the bath- 

 house, Santa Barbara. 



