CLASS PELECYPODA 
149 
sinus; margins of valve thin, smooth. Length, 110; height, 63; diameter, 
50 mm. (Dali.) 
Type in U. S. N. M., No. 110557. Type locality, U. S. S. Albatross 
station 3009, off Concepcion Bay, Gulf of California. 
Range. Off Point Sur, California, to the Gulf of California. 
Family VENERID2E. 
Genus DOSINIA Scopoli, 1777. 
Shell orbicular, compressed, concentrically striated, pale ligament sunk; 
lunule deep; hinge like Cytherea; margins even; pallial sinus deep, 
angular, ascending. (Tryon. S. S. Conch.) 
Type. Dosinia africana Hanley. 
Distribution. Boreal to tropical seas. 
Range in Time. Cretaceous, Pleistocene. 
Dosinia ponderosa Gray, 1838. 
The Analyst., 8:24:309. Sowerby, Thes. Conch. Artemis; pi. 140, fig. 2. 
Shell nearly orbicular, rather compressed, a little broader than high, 
concentrically grooved, grooves almost obsolete in the middle, area of the 
ligament simple, lunule oblong-cordate, concavely impressed; cream color, 
covered with a thin, shining epidermis. (Conch. Iconica.) 
Type in British Museum, Cuming Collection. Type locality, Gulf of 
California. 
Range. San Diego, California, to Payta, Peru. In the Pleistocene at 
San Diego and the Pliocene at Kirker's Pass, Contra Costa County; San 
Fernando, Stanford University and Santa Clara County, California. 
Genus TIVELA Link, 1807. 
Shell triangular, sub-equilateral, 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 some¬ 
times horizontal sinus. (Tryon. S. S. Conch.) 
Type. Venus matroides Born. 
Distribution. West Indies, Mediterranean, Senegal, Cape, India, 
W. America. 
Range in Time. Miocene, Pleistocene. 
Subgenus Pachydesma Conrad, 1854. 
Tivela stultorum Mawe, 1823. 
Linn. Syst. Conch., p. 37; pi. 9, fig. 7. 
Shell equilateral, triangular, thick; convex-depressed; lunule unde¬ 
fined ; posterior extremity, truncated; ligament short, very broad and 
