CLASS GASTROPODA 
131 
5*. debile in being convex and larger. 5'. debilis is very flat, the early 
whorls are smaller and fewer. Length of shell, 38; breadth, 18; height, 
18 mm. (I. S. Oldroyd.) 
Type in Stanford University, Oldroyd Collection. Type locality, San 
Pedro, California. 
Range. Monterey, California, to Todos Santos Bay, Lower California. 
Sinum debile Gould, 1852 
Plate 92, figs. 3, 7 
Boston Journal of Natural History, 6:379. Tryon, Manual of Conchology, 8: PL 24, 
fig. 65. 
T. parva, tenuis, lucida, depressa, mellea, striis numerosissimis obtusis 
volventibus, supernis majoribus, insculpta; spira superficiei generali con- 
gruens; anfr. duobos; apice ad quadrantem diametris sito: angulo ad 
peripheriam obtuso, versus aperturam sensim evanido; labio antice dilatato. 
(Gould.) 
Shell small, much depressed, thin, almost pellucid, pale honey-yellow 
color; whorls two, spire almost coincident with the general surface, apex 
at one-fourth the diameter of the shell; periphery obtuse-angular, becom¬ 
ing more so as it approaches the aperture; ventral surface excavated at 
the umbilical region, with a slight unappressed lamina at that point; margin 
of the aperture having a very slight advance in the outline, as it approaches 
the peripheral angle; surface with very numerous and very delicate, ob¬ 
tusely excavated, revolving striae, much finer on the ventral than on the 
dorsal face. Long diameter, J/% ; short diameter, not quite ; height, % in. 
(Gould.) 
Type in Albany State Museum, Albany. Type locality, La Paz, Lower 
California. 
Range. Catalina Island, California, to Gulf of California. 
Sinum keratium Dali, 1919 
Proceedings of the United States National Museum, 56:354. 
Shell small, white, convex, suborbicular, with a minute subglobular 
nucleus and three subsequent whorls; suture distinct and deep; spiral 
sculpture of sharp, rather regular grooves with wider interspaces crossed 
by fine incremental lines, which in places give a punctate effect to the 
grooves under the lens; the grooves on the base closer and finer; pillar 
lip slightly reflected over an umbilical chink, body with a thin glaze. Long 
diameter, 6.5; shorter diameter, 5 ; height, 3.5 mm. (Dali.) 
1 733 ] 
