208 HYPSOMETEICAL DISTRIBUTION, ETC. 



A few Asiatic species have been collected at great heights. 



Helix (Plectopylis) SMroiensis, over 9000 feet. India. 



Buliminus vibex, YOOO feet. India. 



BuUminus nivicola^ 14,000 feet. India. 



BidiminuH ornatusi 14,000 feet. India. 



Nanina Uratula^ 6000 feet. Ceylon. 



Stenogyra latebricola, TOOO feet. Landoura, Bengal. 



Limnsea Hookeri^ 18,000 feet! Landoura, Bengal. 



Anadenus Schlagintweiti, 16,500 feet. India. 



In Polynesia, Helix hursatella^ a small species, lives at Tahiti 

 between 2000 and 5000 feet altitude. 



In examining the faunas of distant mountainous regions of 

 Europe, we find identical or representative species, which, never- 

 theless do not occur in the intervening plains : for example, 

 Pujja megacheilos^ Italy and Pyrenees. Helix arbustorum, Alps ; 

 and H. Xatartii, Pja-enees. Helix ciliata, Alps ; and H Bec- 

 carii, Abyssinia. On the other hand some of the mollusks of 

 cold countries are found also in more southern regions, but at 

 a greater elevation, so that the conditions of temperature and 

 of vegetation are reproduced ; thus Vertigo alpestris inhabits 

 Scandinavia, and occurs again, upon the Alps only, in Switzer- 

 land. 



These facts have a great importance in connection with a just 

 appreciation of the physiognomy of the quaternary fauna of a 

 determined region. 



As to the bathj^metrical distribution of lacustrine mollusks, 

 we know absolutely very little. The Lake of Geneva has a 

 maximum depth of 1100 feet, with a uniform and constant 

 temperature at all depths. Some crustaceans fo.und at the 

 bottom of the lake are blind, but the Limnaeans have their eyes 

 normally pigmented. Forel says : The deep fauna of the lake 

 consists of a few species belonging to the most of the classes of 

 animals inhabiting fresh water. A certain number of genera and 

 families represented in the littoral fauna appear to be wanting 

 to the abyssal ; but there are no generic types belonging exclu- 

 sively to the latter. Some species of the abyssal fauna, however, 

 are different but analogous to superficial forms — differences which 

 may be attributed to adaptation. Forel and Brot state that the 

 pulmonary chamber of Limnaea abyssicola contains no air at the 

 moment,when it is taken from the water ; but preserved in a jar, 

 the animal behaves like its congeners, coming to the surface to 

 respire, and passing entire hours out of the water. The abys- 

 sinal Pisidiums of the Lake of Geneva and of other Swiss lakes 

 have the following characters in common, their minute size and 

 enlarged beaks, characters which are similar to B. abyssicola 

 of Lake Superior. 



