No. 2328. PLEISTOCENE VERTEBRATES IN UNITED STATES— HAY. 105 



Diagnosis. — Upper incisors broad and unusually thin ; front border 

 rounded. 



The type and only known specimen of this species is a left incisor 

 and a part of the premaxilla (Cat. No. 9197) exposed on a lump of 

 cave earth. It is illustrated on plate 4, figure 20. The width of 

 the tooth is 3.9 mm. ; its thickness only 1.3 mm. On the same lump 

 of clay is an upper incisor, referred to S. carolinensis, whose width 

 is 3.2 mm. and whose thickness is 1.5 mm. The detached tooth re- 

 ferred below to S. hudsonicus is only 2.9 mm. wide, and is 1.5 mm. 

 thick. Teeth of S. caroUnensis nearly as wide as the fossil may be 

 found, but they are thicker. S. niger has broad thick incisors. In 

 both of the species just mentioned the front border of the tooth is 

 rather flat and usually traversed by a shallow groove. In the fossil 

 tooth the front border is rounded. An examination of a series has 

 failed to find any squirrel with teeth so broad and thin as the fossil 

 here described. 



SCIURUS HUDSONICUS (Erxlebcn). 



[ A detached upper left incisor (Cat. 9199) is referred to this 



species. The width is 2.9 mm. ; the thickness, 1.5 mm. The incisors 

 of this species are difficult to distinguish from those of S. caro- 

 Unensis, but the former are on an average distinctly smaller. 



SCIURUS CAROLINENSIS Gmelin. 



On the lump of red clay which bears the type of S. tenvidens 

 there are a part of a right premaxilla and the greater part of the 

 corresponding incisor of S. carolinensis (Cat. No. 9198), The greater 

 diameter of the incisor is 3.2 mm. ; the thickness, 1.5 mm. 



MARMOTA MONAX (Linnaeus). 



Of this species there is a fragment of the left ramus of the lower 

 jaw which contains the premolar and the first molar (Cat. No. 9200). 

 It belonged to a large, heavy-jaw^ed individual. There are present 

 also a well-preserved lower left incisor (Cat. No. 9201), somewhat 

 larger than any found in the collection of recent skulls, and the 

 distal end of a left humerus (Cat. No. 9202). 



Family CASTORIDAE. 



CASTOR CANADENSIS Knhl. 



Of the Canadian beaver there are a fragment of a lower incisor 

 whose width is 9 mm., and an upright third molar (Cat. No. 9203). 



Family CRICETIDAE. 



ONDATRA ZIBETHICA (Linnaeus). 



A single lower left incisor is all that, so far as found, represents 

 this species. The tooth belonged to a small individual. 



