CLASS GASTROPODA 
137 
SECTION MARSENINA Gray, 1850 
Lamellaria rhombica Dali, 1871 
Plate 92, figs. 1, 2 
American Journal of Conchology, 7:122; PL 15, figs. 4, 5. 
Shell pure white, subrhombical in shape, moderately elevated, of three 
whorls. Columella thickened, stout, reflected, narrow, with a groove be¬ 
hind the callus. Whorl appressed against, and slightly flattened below, the 
suture; spire very small, not elevated; apex not above the level of the last 
whorl. Aperture subquadrate, outer lip very much produced, slightly 
angulated above and below. Suture deep appressed. Nucleus smaller than 
in the last; surface of the whorls smooth, without striulae. Lat., .46; long., 
.32; alt., .2 in. (Dali.) 
Type in United States National Museum. Type locality, Monterey 
Bay, California. 
Range. Neah Bay, Washington, to Magdalena Bay, Lower California. 
Genus ONCHIDIOPSIS Berg, 1853 
Shell entirely inclosed by the animal, thin, slipper-like, without spire, 
margin entire. Animal verrucose, with a lanceolate foot. (Tryon, Struc¬ 
tural and Systematic Conchology .) 
Type. O. glacialis M. Sars. 
Distribution. Norway, Great Britain, New Zealand, Mediterranean, 
Philippines, and North Pacific Ocean. 
Onchidiopsis hannai Dali, 1916 
Proceedings, Philadelphia Academy of Natural Sciences, 376. 
The base of the arc of the shell measures 40 mm. long by 32 mm. wide. 
It has much the shape of the bowl of a deep oval ladle and its depth is 
about 15 mm. when in normal position. Its structure is concentric, not in 
circles but in a rounded-quadrate fashion. On the edge of the left side 
behind is a knot-like nucleus. On the inner surface near this nucleus and 
extending for a length of about 12 mm. away from it are two elevated 
straight ridges, which at half their length from the nucleus join to form 
a single stronger ridge, which gradually diminishes and becomes obsolete 
on the inner surface of the disk. The appearance of these ridges suggests 
that if the shell was spirally coiled they would form a columella. The 
outer surface of the shell, to which the mantle adheres tenaciously, is 
smooth, but undulated by more or less irregularly disposed concentric 
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