WEST COAST PULMONATA. 365 



to a great extent; that is, the great gap in the coast ranges 

 made by the outlet of the two chief rivers of California, 

 allows the sea breeze to penetrate freely to the in- 

 terior, carrying moisture and coolness high up on the 

 Sierra Nevada. There are other *• wind-gaps" at Monterey 

 and Bodega Bays, by which the wind passes less freely 

 through the Coast range. 



Previous to 1869, when I wrote the article on the distri- 

 bution of our land shells for the American Journal of Con- 

 ch ology, I had collected along the coast border and in the 

 Santa Cruz Mts. up to about 2,800 feet altitude. As 

 then stated, judging from what was known of their distribu- 

 tion in the Sierra Nevada and Eocky Mts. of Montana, 

 I supposed that the coast range must be well stocked up to 

 the summits with these animals, as lime in fossil beds and 

 plenty of moisture, with no ]3ermanent snow, were known to 

 characterize them almost everywhere. But the real distri- 

 bution has proved so different in t!ie bay region, that I am 

 induced to describe it in detail for each county, taking them 

 up as they are situated — in general — east, south, west and 

 north of San Francisco Bay. The list of species here given 

 is arranged to show this distribution, and to save repetition 

 of names, the species are referred to by numbers. Of this 

 list 15 species are nearly or quite identical with Sierra species, 

 six of them indeed being of that boreal group, in great part 

 circumpolar, which doubtless reached both ranges from the 

 north. The largest is M. armigerits, which differs consid- 

 erably in the Sierras, as far as known, but being quite small, 

 gives little room for specific distinctions, as is also true 

 of the remaining species, which are of the simpler, 

 plainer groups. These identical species are marked ^. 

 The most interesting of the species is H. cUahloan- 

 sis, as the nearest approach to a proof of the deriva- 

 tion of the Coast Range banded Helices from Sierra 

 Nevada species north of lat. 35^. But although it 

 might have been derived from shells washed down the San 



