458 RODENTIA 



and two external enamel-folds ; the stomach has a large glandular 

 mass situated to the right of the oesophageal orifice ; the anal and 

 urethro-genital orifices open within a common cloaca ; the tail is 

 broad, horizontally flattened, and naked ; and the hind feet are 

 webbed. One or two species, Pakearctic and Nearctic. 



Zoologists are not yet of accord as to whether the European 

 and American Beavers should be regarded as distinct species or as 

 local races ; the general concensus of opinion being in favour of 

 the latter view. 



The European Beaver (C. fiber) was at one time an inhabitant 

 of the British Isles, having been found, according to Pennant, in 

 certain Welsh rivers so late as the twelfth century, while subfossil 

 remains of it occur in the peat-beds of many parts of the country. 

 In Scandinavia Beavers are still found in the neighbourhood of 

 Arendal. Isolated pairs are occasionally met with on the banks of 

 the Rhone, Weser, and Elbe ; and a considerable number are kept 

 in a park belonging to the Emperor of Austria, on the banks of 

 the Danube. They also occur sparingly in Russia and Poland, 

 in the .streams of the Ural Mountains, and in those which flow 

 into the Caspian. They live in burrows on the banks of rivers, 

 like the Water -Rat, and show little of the architectural instinct 

 so conspicuous in the American form, but this may be owing to 

 unfavourable external conditions rather than to want of the 

 faculty ; for there is a well-authenticated instance of a colony of 

 Beavers, on a small stream near Magdeburg, whose habitations 

 and dam were exactly similar to those found in America. 



The American Beaver (C. canadensis) extends over that part of 

 the American continent included between the Arctic circle and 

 the tropic of Cancer ; owing, however, to the gradual spread of 

 population over part of this area, and still more to the enormous 

 quantity of skins that, towards the end of last and the beginning 

 of the present century, were exported to Europe, numbering about 

 200,000 annually, this species is in imminent danger of extirpation. 

 It is distinguished from the European Beaver by the shorter and 

 somewhat wider nasals. 



Remains of extinct species of Castor occur in the Pliocene of 

 Europe, and in the North American Miocene ; the one from the 

 last-mentioned deposits being of small size, and separated by some 

 writers as Evcastor. 



Extind Genera. — A very large Beaver known as Trogontheriwm 

 (Diobroticus), and distinguished by the nature of the enamel-folds of 

 the molars, occurs in the Upper Pliocene and Pleistocene of Europe. 

 ( 'haJicomys (Steneofiher) is a considerably smaller form from the 

 .Miocene of Europe and the United States, distinguished from all 

 existing Rodents by the presence of an entepicondylar foramen in 

 the humerus. Palceocastor, of the North American Miocene, is allied. 



