42 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Genus THAIS Bolten, 1798 
The genus Thais of Bolten is well-constituted, containing a very uni¬ 
form assembly of species which, with a single exception of a closely re¬ 
lated Acanthina, will remain in the genus as at present understood. The 
genus Thais will comprise even more than was supposed by its author. The 
small lirations or tubercles on the pillar near its anterior end are often 
present or absent indifferently in specimens of the same species, or even 
in the same individual at different ages, and are of vastly different value 
from the permanent plaits on the pillar, which is present at all ages of the 
individual. The sculpture is also, as is well-known, liable to vary from 
smooth to imbricate or nodulous within the limits of the species. The 
prevalent sculpture in the group is spiral, modified into ridges, scales, 
nodes, or even spines. The species represented on our coast are in the 
Subgenus Nucclla Bolten. 
Type. Thais lapillns Linnaeus. 
Distribution. Atlantic and Pacific coasts of North America. 
Subgenus Nucella Bolten, 1798 
Thais lamellosa Gmelin, 1792 
Plate 38, figs. 1, 2, 4; Plate 35, fig. 7 
Systerna Naturae , 7:3498. Proceedings of the United States Natioyval Museum, 
49:563; PI. 74, figs. 5-8. 
Testa subplicata transversim costata sulcata tuberculata lamellosa 
brunneo alboque fasciata. (Gmelin.) 
Shell fusiform, thick; spire elevated; apex subacute; whorls five to 
seven, convex or angulated, with one or more prominent spiral ridges on 
angular part of whorl; suture impressed, distinct; aperture ovate or ellip¬ 
tical; outer lip effuse, generally denticulate; inner lip incrusted, smooth; 
canal short, curved backward; umbilicus subperforate. Long., 34; lat., 20; 
body-whorl, 26; aperture including canal, 22.5 ; canal, 6 mm. (Arnold.) 
Range. Port Clarence, Bering Strait, and southward on the west to 
Sado Island, Japan Sea; on the east to the Aleutian Islands, and Santa 
Barbara, California. Fossil: Pleistocene and Pliocene of California and 
Oregon. 
Shell large, heavy, smooth, with rounded whorls and deep though 
appressed sutures, resembling a very thick and heavy Chrysodomus. The 
measurements are about the same as in the typical form. 
T\pe in United States National Museum. Type locality, Cook’s Inlet. 
Range. Known only from type locality. 
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