242 U. 8. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



Tribe II. ARCTOMYINA. The first upper molar equal in length to the second, and about one- 

 half or one-third the size ; swollen at the base ; conico-acuminate at the apex, truncate at the 

 point, compressed and more or less lobed, more rarely simple but always with a slight pit 

 behind. The crowns of the larger molars, except the last, are trigonal, wedge-shaped, with 

 two shorter ridges formed by the anterior and posterior edges of the tooth itself, and two inter 

 mediate larger ones, generally quite elevated and acute. The anterior dentiform tubercles of 

 the lower molars exceed almost twice the height of the bases of the crowns. The ridges of the 

 soft palate between the molars almost double the molars in number and considerably approxi 

 mated. The third finger always longer than the rest. Claws considerably elongated, trigonal, 

 and dilated at the base ; moderately curved. 



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