272 WEST COAST SHELLS 



Orcohelix sfrii/osa^ Gld., the 

 Mountain Snail, is the most numer- 

 ous ot all the snails found between 

 the Rocky Mountains and the Sier- 

 ra Nevada Range. It assumes very 

 many forms, some ot which have been described as 

 separate species. One ot these forms is shown in 

 Figure 265, which by some would be classed as O. 

 Hayde??^, Gabb. Concerning this point I quote from 

 Mr. Binney, who says, "I have received from Mr. 

 Henry Hemphill specimens of Helix Haydeni with 

 the animal, and so variable that I am convinced of 

 its being a variety of strigosa'' Mr. Pilsbry inclines 

 to a separation ot the species, though admitting their 

 close relationship. As the forms are so difficult of 

 separation I see no advantage in such a book as this 

 of trying to distinguish between them. The specimen 

 for the figure was selected from a large number of 

 typical shells, because it seemed to be intermediate 

 between the greatly varying forms. 



The Mountain Snail abounds especially in Idaho 

 and Utah, and some varieties are found far up on 

 mountain sides, even as high as 8500 feet. The shell 

 has a broad umbilicus, a nearly circular aperture, and 

 a sharp lijx The whorls are about five in number, 

 and in most specimens the spire is low. The average 

 diameter is about three-fourths of an inch, though 

 some varieties are much smaller. 



Perhaps no other shell in the country has so many 

 varieties as this movmtain snail. Some of them are 

 almost smooth, some ribbed spirally, others trans- 

 versely. Some are nearly white, others are marked 



