94 RODENTS. 



a distinct genus, but likewise a separate subfamily, although they were till recently 

 included among the true squirrels. Their skulls are remarkable for the elongated 

 form of the region of the face, while the forehead is much broader than in any 

 other type ; and the process defining the hinder border of the socket of the eye is 

 so elongated as to cause the eye to be almost surrounded by bone. In the upper 

 jaw there may be either one or two pairs of small premolar teeth ; and the molars 

 are much more complex than in any other squirrels, closely approaching those 

 of the dormice in structure; the upper molars having only three transverse 

 plates, instead of the four characterising those of the other members of the 

 family. 



One of the prettiest representatives of the gH)up is Whitehead's pigmy squirrel 

 (N. whiteheadi), from North Borneo, in which the head and body measure only 

 about 3J inches in length, and the ears are surmounted by extraordinarily long 

 tufts of black and white hairs, apparently more elongated than in any other squirrel. 

 This little animal, which is grizzled olive grey in general colour, may be commonly 

 seen running up and down the trunks of the forest trees on Mount Kina Balu. 



THE SEWELLELS. 

 Family HAPLODONTID^E. 



These North American Rodents differ so remarkably from the other living forms 

 that they are regarded as constituting a family by themselves, of which the nearest 

 affinities are supposed to be with the Squirrel family. They differ from all the 

 members of that family by their extremely flattened and broad skulls, in which 

 there is no postorbital process defining the hinder part of the upper border of the 

 socket of the eye. The molar teeth have no roots, and the first pair of premolars 

 in the upper jaw are exceedingly minute. 



Common The common sewellel (Haplodon rufus) is an animal measuring 



SeweiieL about a foot in length, exclusive of the stump-like tail, which measures 

 little more than an inch. The general colour of the fur is brown, more or less 

 mingled with black, with the under-parts greyish ; the front teeth being yellow. 

 The general form of the animal is short and clumsy, with the body relatively large 

 and cylindrical. Dr. Hart Merriam observes that " this singular animal, which has 

 come down to us as a relic of the past, and has no near affinities with any existing 

 group, inhabits a narrow strip of country on the north-west coast of the United 

 States. All the specimens thus far obtained have come either from Oregon or 

 Washington, or from the Chilukweyuk River near its junction with the Fraser, 

 just across our border in British Columbia." The animal lives in companies, 

 constructing burrows in moist ground. 



Caiifornian The Californian sewellel (H. major) the mountain-beaver of 



sewellel. the inhabitants is a larger animal, measuring 16 inches in length, 

 with greyish brown fur above. These Rodents inhabit the Sierra Nevada, and are 

 largely aquatic in their habits. Mr. C. A. Allen, by whom the species was 

 discovered, writes that they " live in small colonies, and inhabit wet ground where 

 there is plenty of running water. They are very compact and strong, with a head 



