[he Nautilus. 



Vol. XXV. APRIL, 1912. No. 12 



OBEOHELIX COLONIES IN COLOBASO. 



BY JUNIUS HENDERSON. 



The native species of land snails in Colorado are mostly small — 

 from the size of Pyramidula cockereUi down to Vertigo and VaUonia. 

 The only known exception is the genus Oreoheli"x, which is much 

 better represented, both in numbers of species and abundance of in- 

 dividuals, than has generally been supposed. My first experience 

 with the genus was along the eastern foothill belt of the Rocky Moun- 

 tains, the eastern limit of its range in Colorado. There I found 

 Oreohelix strigosa depressa Cockerell (then considered 0. strigosa), 

 very generally but sparingly distributed, never obtaining more than 

 half a dozen live or freshly dead specimens. Several facts led to the 

 natural conclusion that the genus was approaching extinction in Col- 

 orado. (1) The scarcity of live specimens along the foothills. (2) 

 The occurrence of large numbers of fossil specimens in a small ex- 

 posure near Boulder, taken in connection with the widespread belief 

 in a marked desiccation of the West and Southwest since middle 

 Pleistocene time, which would make conditions less favorable for 

 these snails. (4) IngersoU's report (Hayden Survey, Ann. Rept., 

 1874, p. 396; Binney's Land Shells, p. 166) that dead 0. cooperi 

 were abundant in North and Middle Park, but that live ones were 

 not common. (4) Numerous dead shells received from various lo- 

 calities west of the Continental Divide, with no live ones. (5) The 

 occurrence of 0. haydcni fossil in large numbers near Glenwood 

 Springs, with no live or freshly dead ones reported. 



More recent discoveries have rendered that view wholly untenable. 



