ACADEMY OP SCIENCES. 171 



On Shells of the West Slope of North America. 



No. II. 



BY J. G. COOPER, M. D. 



At our last meeting, Mr. Henry Hemphill presented about sixty species of 

 land and fresh water shells, chiefly from Nevada, Utah, Idaho, Oregon aud 

 Washington Territory, among which were ten or twelve not before in the 

 Academy's collection, besides many of much interest on account of new locali- 

 ties, or from exhibiting greater or le?s amounts of variation, aud thus showing 

 the connection between permanency of specific characters and wide geograph- 

 ical range of distribution. 



I therefore offer the following notes on the most important additions thus 

 made to our knowledge of these creatures, with a few others made by myself 

 since the article on this subject published on p. 150 of this volume, which 

 brought it down to this year. 



1 take this opportunity to thank Mr. Tryon for his complimentary notice of 

 ray synopsis on p. 92 of this volume. In the Journal of Conchology, he 

 considers it " full of errors," because I reduce many of his " species " to varie- 

 ties ; but admits that it will please all conservative conchologists, which is just 

 what I hoped of it. He blames me, however, for considering any western 

 species identical with eastern, in which opinion I followed almost exactly his 

 own views, given in the same Journal, Vol. I, pp. 165, 247. 



ISphferium Spokani Baird. Young ones found near Spokan 

 E., W. T. {Hemphill), show that this is probably a good species, more circular 

 than any figured by Prime. 



2 P i s i d i u m c o m p r e s s u m Prime. Found plenty at White 

 Pine, Nevada, and Owen's River, California, by Hemphill and quite distinct 

 from the Clear Lake form. 



SPisidium occidentale Neivc. Specimens from Portland, 

 Oregon, and the San Diego mines, are undistinguishable from those found here. 



4 Succinea Oregonensis Lea. Also found at San Diego mines, 

 while near the town, S. r u s t i c a n a Gld., is the prevailing form {Dunn). 

 1 am doubtful, however, whether these can be maintained as distinct species, 

 many being intermediate. 



5Macrocyclis Voyana Newc. San Diego, Dunn, Alameda 

 County, Yates, Hemphill. Common at San Diega, and are twice as large 

 as types, but similar in surface and flatness, though the mouth is less 

 twisted. Very rare in Alameda, and intermediate. The common smooth spe- 

 cies {concava ?) is found with it here, but not at San Diego. The animals differ 

 in the two species, as found near together at this bay, and from M. Vancouver, 

 ensis, of Oregon. 



GAnguispira solitaria Say. Specimens brought from the 

 Coeur d'Alene Mountains, Montana, by Hemphill, leave no longer any doubt as 

 to this being the true solitaria, and distinct from A. Cooperi found near it. 

 Proc. Cal. Acad. Sci., Vol. IV.— 13. January, 1872. 



