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66d 



MONOGRAPHS OP NORTH AMERICAN RODBNTIA. 



erally. Some of them are colorless, like the hairs upon the face ; and, indeed, 

 there is upon the bacU of the fore arm n special tuft of long colorless bristles, 

 quite like the shorter whiskers. The long scattered hairs of the upper parts 

 are black, giving a darker tone to the reddish-brown or chestnut of these parts ; 

 on the under parts, the cast is more grayish. The basal portion of the pelage 

 is dark plumbeous above, paler or grayiaii below. I have not sufficient mute- 

 rial to indicate the range of individual color-variation. Some specimens are 

 said to be quite blackish. None of those examined show a pure white thront- 

 patch, spoken of by some writers ; but it is indicated in some cases by a few 

 white hairs. The hands, feet, and ears appear whitish, at least in contrast 

 with the general dark body colors ; and the short pelage of the lips, anus, 

 and priEputial sheath is usually more or less whitened. The claws are nearly 

 colorless; the incisors are yellow. 



The anus is situate a considerable distance from the root of the tail. In 

 the male, owing to the size of the os penis, the sheath of the penis forms a 

 large conical projection immediately in front of the anus, and is directed more 

 or less backward i it is hairy, with a long, slender, terminal pencil. The penis 

 may be readily protruded in alcoholic specimens. There is no appearance of 

 a glans. The bone extends to the end of the member; it is elsewhere 

 described. I have seen no female specimens. There are said by Richardson 

 to be six mammBC, tiie position of which is indicated by brown circular marks, 

 the anterior pair being situated between the tore legs. 



B. — DE8CBIPTI0N OP TIIE TEETH. 



The incisors offer nothing specially noteworthy. They are very stout 

 for the size of the animal, their anterior faces perfectly smooth, convex in 

 both directions, the sides much bevelled. The under, as usual, protrude 

 farther than the upper, and also incline farther forward as they ascend, the 

 upper being perpendicular. The upper are separated from each other at base 

 by a considerable alveolar interval, but incline toward each other, their points 

 being in contact ; the under are more nearly parallel. 



The molar series occupies a more posterior position than may be 

 usual in Rodents, the anterior true molar being opposite the middle of 

 the skull. The whole series is about one-fourth as long as the skull. The 

 inner alveolar border is parallel with its fellow; the outer is slightly 

 divergent, owing to increase in size of the teeth from behind forward, — from 



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