OF CONCHOLOGY. 211 



ON THE DISTRIBUTION AND LOCALITIES OF WEST 

 COAST HELICOID LAND SHELLS, &C. 



BY J. G. COOPER, M.D. 



One remarkable fact, which strikes the attention of collectors 

 in every branch of zoology and botany west of the Rocky 

 Mountains, is the limited and often isolated location of most of 

 the species, compared with their extensive range in the Atlantic 

 States. This, however, is more apparent than real in many in- 

 stances, for many species have been ascertained to occur along 

 the whole of our coast .from north to south, and even much 

 farther in both directions. The real peculiarity in their distri- 

 bution is, that in travelling from the coast inland, the collector 

 passes over a number of parallel zones, each having peculiar 

 species, with few common to them all. He is in fact like a 

 traveller ascending a lofty isolated peak, who finds a succession 

 of faunas and floras rising one above the other until he reaches 

 the limits of perpetual ice where neither can exist. On the 

 other hand, he might start at the straits'of Fuca, and travelling 

 southward, gradually rising higher up the mountain slopes, find 

 almost the same fauna and flora at 6000 or 8000 feet elevation 

 in the latitude of San Diego, (about 32° 30'), as he started with- 

 in lat. 49°. But at its southern extremity the belt is but a few 

 miles wide, and most of the animals common to the two ends 

 are such as have great powers of locomotion, while the plants 

 are such as have had their seeds transported by migratory birds. 

 There are merely enough of the northern species to demonstrate 

 the fact that the zones of distribution run nearly parallel to the 

 coast, and along the flanks of the mountain ranges, not parallel 

 with the degrees of latitude, as they do in more level countries, 

 nor transversely either, but obliquely, at an angle between them 

 and the meridians of longitude. The routes of travel, however, 

 do not follow the zones of distribution, but on account of the 

 gradual raising of the latter towards the south, cross them 

 obliquely, so that the traveller passes from one zone to another, 

 though less rapidly than if going directly inland from the coast. 



