74 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



The dental formula may be given at incisors ^, canines J^T, premolars ^, molars ~, = ^ 

 = 44. The anterior upper incisors project nearly horizontally, and are axe-shaped, the crown 

 being sub-compressed, widened suddenly beyond the neck, and having a distant resemblance to 

 the anterior incisor of the shrews. Those of opposite sides lie very close together, making the 

 two halves of a kind of spoon. Next succeeds a very slender thread-like incisor, implanted 

 vertically, and then a long canine-like incisor in immediate contact, and almost as much 

 developed as the canine of Talpa. This tooth has a small spur on its trenchant extero-posterior 

 edge. Next, after a considerable interval, comes the diminutive canine with a simple fang, 

 and then succeed three compressed premolars with double fangs, a central large-pointed lobe 

 and two basal ones to each. The last premolar and the three molars are in close contact ; the 

 anterior premolars, the canine, and the third incisors, are all separated from each other by con 

 siderable intervals. 



In the lower jaw the three incisors are directed horizontally, forward, the two inner ones com 

 bining closely with their fellows of opposite sides, to form one continuous spoon-shaped projec 

 tion, with difficulty separable into its four components. The exterior incisor is small and 

 thread-like, with difficulty discernible in its situation close to the second incisor. The canine 

 is rather large and distinct, and has a posterior basal fang ; the premolars are somewhat like 

 the upper ones, and exhibit the same conditions as to interspaces. 



Measurements. 



