CLASS PELECYPODA 
31 
Range. San Francisco Bay to San Diego, California. In the Plio¬ 
cene of San Fernando and the Pleistocene at San Pedro and San Diego. 
Yoldia limatula Say, 1831. 
Plate 19, figs. 1, la, lb. 
Amer . Conch., 163: pi. 12, Hanley, Mon. Nuculidce, pi. 1, fig. 9. 
Shell transversely elongated subovate, green olive, nearly pellucid, 
smooth, polished, with slight inductions of increment; beaks not promi¬ 
nent above the curve of the hinge margin; hinge margin anteriorly 
abruptly compressed; the compression not reaching the tip; rectilinear 
nearly to the tip which is a little recurved; posteriorly almost regularly, 
but obtusely arcuated; posterior margin regularly rounded; anterior mar¬ 
gin somewhat rostrated, not truncated; within a little perlaceous; margin 
entire; line of the teeth slightly interrupted and a little angulated at the 
fosset, extending more than two-thirds of the length of the shell, recti¬ 
linear before and behind; teeth prominent, numerous, acute, much angu¬ 
lated at their bases and longer than the breadth of their bases; fossette 
triangular, short, rather small, and but little oblique. (Say.) 
Type in British Museum? Type locality, Nahant, Massachusetts, from 
stomach of a fish. 
Range. Arctic Ocean to San Diego, California. Also Atlantic. 
SECTION CNESTERIUM Dali, 1898. 
Yoldia scissurata Dali, 1898. 
Plate 5, fig. 2. 
Trans. Wagner Inst. Sci., 3; part 4:595. Cal. Acad. Sci. Mem., 3:1903. 
Shell rather small, oval, compressed, very thin, translucent, only 
slightly narrowed posteriorly; umbones minute, slightly anterior to middle, 
the anterior margin is evenly convex; a thin lamina runs along the anterior 
margin from the umbo to the end of the shell, a much narrower one also 
occurs on the posterior margin; surface sculptured concentrically as in 
F. coo peri, except that this incised sculpture is not in harmony with the 
incremental lines; hinge and teeth similar to Y. cooperi. Length, 20.4; 
height, 10; diameter, 4 mm. (Arnold.) 
Type in U. S. N. M. Type locality, St. Paul, Kodiak Island, Alaska. 
Range. Arctic Ocean to Puget Sound. In the Pleistocene at San 
Pedro, California. 
Yoldia seminuda Dali, 1871. 
Amer. Journ. Conch., 7:153. 
Shell obscurely lozenge-shaped, elongate, covered with a polished, 
glossy, olivaceous epidermis. Valves compressed, umbones inconspicuous; 
