Five Species of Vespertalio. 55 



the back, and all tipped with white, giving it a peculiarly hoary 

 aspect. There is a small whitish hairy patch near the first or 

 elbow joint of the wing membrane, and another at the base of 

 the thumb, and in some, a third at the base of the fourth pha- 

 lanx, the remainder of the membrane above being naked. 

 Beneath, the lips and lower jaw are dusky black, throat and 

 neck pale yellowish. At the insertion of the wings is a white 

 mark as in V. noveboracensis, on each side, between which 

 the fur is dusky brown tipped with white, like the upper parts. 

 Lower down it becomes much mixed with pale tawney, Avhich 

 predominates on the flanks, and extends, forming a hairy bor- 

 der of half an inch wide up the membrane, to the origin of 

 the phalanges. The remainder of the wing and interfemoral 

 membranes naked. 



The sides of the interfemoral membrane are sustained by a 

 bony process (os calcis ?) three fourths of an inch long, project- 

 ing in a curved line, and articulated with the tibia. This is not 

 peculiar to the species, but is more than usually apparent. 



Incisors -^- canines -^- molars 4-r-=30. 



6 1 — 1 5 — 5 



. Total length 4.3 inches. 



Tail - 1.8" 



Fore arm 2.0" 



Tibia 0.9" 



Spread 15 . " 



I have no doubt of the identity of this Bat with the pruino- 

 sus of Say, as well as of Richardson, who has described its 

 external markings with minuteness and accuracy. The differ- 

 ence in size remarked by Dr. Richardson in his specimen is 

 not greater than I have observed betvyeen different specimens 

 of the smaller species ; but the dental formula given by him, 

 is materially unlike that which I, after repeated examination, 

 have laid down as above. In fact, this and the following spe- 

 cies agree strictly in all the peculiarities of their dental system, 



