360 PROCEEDINGS OF THE NATIONAL MUSEUM, vou. xxxi¥ 
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PELECYPODA. 
Genus SEMELE Schumacher. 
SEMELE GAYIJI, new species. 
Plate XXXII, fig. 5. 7 
Description.Shell averaging about 14 mm. in latitude, subquad- 
rate in outline, quite a little longer than wide, moderately inflated, 
rather thin, inequilateral, subequivalve. Beaks not prominent, turned 
shehtly forward, situated about three-fifths length of shell from an- 
terior end. Posterior margin slightly curved, sloping off rapidly 
toward anterior extremity, which is subangular and situated about 
one-third height of shell from the base; posterior fold very faint; 
anterior dorsal margin slightly depressed; anterior extremity more 
evenly and less sharply rounded than posterior; base evenly arcuate. 
Surface sculptured by numerous regular, fine, sharp concentric 
ridges, each with abrupt side toward the beak, the opposite side slop- 
ing, and each appearing to overlap its predecessor; in the larger 
specimens one or more well defined concentric grooves are sometimes 
found near the periphery. Interior showing well defined mantel 1m- 
pression parallel with margin and about one-sixth height of shell 
away from it; interior also coarsely radially grooved. 
Dimensions —Of imperfect right valve (type), restored; length, 
17 mm.; latitude, 14 mm.; diameter of single valve, 2.8 mm. 
Notes.—This species 1s apparently nearest related to S. rubropicta 
Dall (recent range, Washington to Mexico) of any of the living 
forms. It may be distinguished from the latter by its smaller size, 
finer and more regular concentric ribs, and lack of any external radi- 
ating sculpture. With the exception of S. rubropicta, S. gayi is 
more abruptly truncated posteriorly than any other member of the 
genus on the west coast. | 
Named in honor of Mr. Harold 8. Gay, who first discovered the 
locality from which this species and its interesting associated fauna 
come. . 
Type.—tImperfect right valve, Cat. No. 1654385, U.S.N.M.  ~ 
Locality.—Santa Cruz quadrangle, San Mateo County, locality No. 
between headwaters of San Lorenzo River and Pescadero Creek. 
H. S. Gay, R. Arnold.) 
GASTEROPODA. 
Genus TRITONIUM Link. 
TRITONIUM NEWSOMI, new species. 
2 
( 
Plate XXXII, fig. 6. 
Description.Shell averaging about 18 mm. in altitude, subquad- 
rate in outline; spire elevated, apex acute; whorls 5 or more, the 
the two upper minute; the others rounded and sculptured by 4 re- 
volving and about 14 narrow, ridge-like axial cost, the intersections 
