CLASS PELECYPODA 
93 
L. (A) formosa Jeff., from the Canaries, but differs in the following 
details; the anterior transverse ripples, the central nodulous ray, and the 
radial ridge below the posterior dorsal area are more vertically directed; 
on the latter area there is only faint indication of the radial ribbing which 
in L. formosa is distinct and minutely spinose; the anterior end is longer 
than the posterior, while in formosa the reverse is the case; the coloration 
of the periostracum is olivaceous green while in formosa it is ferruginous 
brown. Length, 23; height, 15; diameter, 12 mm. (Dali.) 
Type in U. S. N. M., No. 267171. Type locality, off Santa Barbara 
Channel, California. 
Range. Known only from the type locality. 
Subgenus Entodesma Philippi, 1845. 
Lyonsia inflata Conrad, 1837. 
Jour. Acad. Nat. Sci. PJiila., 7:248; pi. 19, fig. 10. 
Shell sub-elliptical, inflated; concentric rugae distinct; ligament margin 
convex; basal margin gibbous; posterior extremity truncated; cardinal 
appendage dilated. (Conrad.) 
Type in Acad. Nat. Sci. Phila. ? Type locality, Guayaquil, Ecuador. 
Range. In sponges, Vancouver Island, British Columbia, to Guaya¬ 
quil, Ecuador. 
SECTION AGRIODESMA Dali, 1909. 
Lyonsia saxicola Baird, 1863. 
Proc. Zool. Soc., p. 70. 
Shell oblong-ovate, gibbous in the center, produced anteriorly, com¬ 
pressed posteriorly and gaping. The beaks are large and incurved; it is 
covered with an olive-colored epidermis, which is striated transversely. 
The ventral margin is gaping and flexuous. The substance of the shell, 
without being very thin, is exceedingly brittle and cracks very easily. 
The ossicle covering the front of the internal cartilage is strong and well 
developed. Length, 100; height, 50; diameter, 35 mm. (Baird.) 
Type locality, Esquimalt Harbor, Vancouver Island. 
Range. Aleutian Islands to San Pedro, California. 
Lyonsia scammoni Dali, 1871. 
Amer. Jour . Conch., 7:142; pi. 16, fig. 3. 
Shell equilateral, inequivalve, sub-ovate. Left valve slightly the smaller. 
Shell tumid, umbos inconspicuous, nearly in the middle of the shell. 
Interior with a brilliantly pearly, white nacre; hinge margin narrow, 
nearly straight; interrupted under the beaks; right valve with a small, 
