84 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
faint incremental lines; base imperforate, aperture lunate, simple, the 
margin entire and continuous. Height, 2; diameter, 0.75 mm. (Dali.) 
Type in United States National Museum, No. 212731. Type locality, 
St. Paul Island, Bering Sea. 
Range. Pribilof Islands, Bering Sea. 
Genus SKENEOPSIS 
Description of genus not found. 
Skeneopsis alaskana Dali, 1919 
Proceedings of the Biological Society of Washington, 32:251. 
Shell minute, resembling S. planorbis Fabriciius, but smaller, more ele¬ 
vated, and with a much smaller umbilicus; whorls two and a half, pale 
greenish white, rounded; suture deep, not appressed; sculpture only of 
more or less evident concentric fine wrinkles, more conspicuous on the top 
of the whorl; aperture circular, simple, umbilicus deep, with about one- 
fifth of the diameter of the last whorl; operculum horny, multispiral. 
(Dali.) 
Type in United States National Museum, No. 271717. Type locality, 
St. Paul Island, Bering Sea. 
Range. Pribilof and Unalaska Islands, Alaska. 
Genus AMPHITHALAMUS Carpenter, 1865 
Testa Rissoidea, nucleo magno; apertura labio producto, labro sub¬ 
postice juncto, subito in adulta contracto. (Carpenter.) 
Type. Amphithalamus inclusus Carpenter. 
Distribution. California and Japan. 
Amphithalamus inclusus Carpenter, 1865 
Annals and Magazine of Natural History, scr. 3, 15:181. Proceedings of the United 
States National Museum, 41:264; 2. 
A. testa minuta, lata, solidiore, pallide rufo-fusca; vertice mamillato; 
anfr. nucl. uno et dimidio, quoad magnitudinem permagnis, minutissime 
et confertissime spiraliter et radiatim striolatis; anfr. norm, iii., laevibus, 
subplanatis, suturis impressis; basi subangulata; costa peripherica rotun- 
data, haud extante, interdum in spira se monstrante; costa altera circa 
regionem pseudo-umbilicarem; labro acuto, haud contracto; labio testa 
adolescente normali, dein a pariete separata, sinum posticum suturam 
versus formante, t. adulta valde separata, regionem quasi umbilicarum 
magnam formante; ad labrum subito fere perpendiculariter, subpostice 
juncto; operculo tenuissimo. Long., .04; long, spir., .02; lat., .03 poll. 
(Carpenter.) 
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