CLASS PELECYPODA 
141 
forated by an orifice, which pierces it in the vicinity of the mouth. The 
edges of this orifice project from the general surface, and it is lined with 
close-set, small papillae. At about the same distance from the posterior 
end is another tubular perforation, holding a similar relation to the anus; 
which has, however, plain edges, and is not internally papillose. (Dali.) 
Type. Chlamydoconcha orcutti Dali. 
Distribution. Known only from California. 
Chlamydoconcha orcutti Dali, 1884. 
Science, 4:76, p. 50. Bernard, Ann. Sci. Nat., Zool. (8), 4; pi. 1, 2. 1897. 
The shells are enclosed in two little sacs in the substance of the 
mantle. The umbones are near together, apparently connected by a brown 
gristle resembling an abortive ligament, and are nearly over the heart. 
The valves are about 10 mm. long and 1 mm. wide, destitute of 
epidermis, prismatic, or pearly layers. There are no muscular or pallial 
impressions, no adductor, hinge, or teeth. The embryonic valves are 
retained like two tiny bubbles on the umbones. (Dali.) 
Type in U. S. N. M. Type locality, San Diego County, California. 
Range. Monterey Bay to False Bay, San Diego County, California. 
Family CARDIIDiE. 
Genus CARDIUM Linmeus, 1758. 
Shell ventricose, close or gaping posteriorly; umbones prominent, 
subcentral; radiately ribbed; margins crenulated; pallial line more or less 
sinuated. (Tryon. S. S. Conch.) 
Type. Cardium costatnm Linnaeus. 
Distribution. Worldwide; from seashore to 140 fathoms. 
Range in Time. Upper Silurian to Pleistocene. 
Subgenus Traciiycardium Morch, 1853. 
Cardium quadragenarium Conrad, 1837. 
Jour. Acad. Nat. Sci. Phila., p. 230; pi. 17, fig. 5. 
Shell cordate, subequilateral, ventricose, thick; ribs forty to forty-two, 
prominent, subangular, flattened at the sides, with a series of small 
tubercles, which, on the anterior side, are largest, and placed in the 
middle of the ribs, but elsewhere on the posterior angular margin of the 
ribs; umbo broad, prominent; beaks not oblique; tubercles elevated on 
the posterior slope; color pale yellow, with fulvus spots and zones; 
posterior margin direct, deeply serrate. Height, 3 inches. (Conrad.) 
Type locality near Santa Barbara, California. 
