INTRODUCTION. XI 



structure. The skeleton of a bat is exjiressive of lightness and 

 tenuity' The bones of the common Brown Bat ( V. subidatus), 

 from which this description is taken, weighed but eleven grains. 



The skull is of proportionate large size, rounded at cranium 

 The parietal crest, generally faintlj produced, is frequently 

 entirely absent ; at the superior angle of occipital bone a faintly 

 defined triangular patch is seen in those skulls where the temporal 

 foss£e on either side have not extended quite the length of the 

 side of cranium. Orbit incomplete ; temporal fossae very large ; 

 zygomata perfect, generally slightly curvilinear, somewhat de- 

 pressed in centre. Anterior nares large, sub-circular, extending 

 back on the palate to a level with the canine teeth. Intermaxillary 

 bones rudimentary and not meeting in front. The bones of the 

 cranium are without diploe, and the interior of the skull without 

 tentorium. Auditory bullae (viz., the circular appendages to the 

 external meatus) very large. Occipital condyles broad ; fora- 

 men magnum large, sul>oval, somewhat depressed. The maxillary 

 bones are stout, and support all the teeth, excepting the incisors, 

 which are held in position by the inter-maxillary bones. 



The lower jaw is stout, receding at symphysis, where it is very 

 high, and extends backwards to a level with the 2d premolar 

 tooth ; coronoid process high, blunt, strongly marked externally 

 to its base with the concave surface for the insertion of temporal 

 muscle. The anterior border is vertical, the superior and pos- 

 terior are slightly oblique, ending in the condyloid process ; the 

 articulating head of which is arranged transversely to the axis 

 of the bone. The ramus of the jaw is turned slightly outward, 

 and is thin and compressed. A large hamular process is con- 

 .spicuous immediatel}" inferior to the articulating surface. 



The teeth are of varialjle number — being in some species as 

 low as 30, in others as high as 38. This variation, combined with 

 differences in their contour, furnish characters of great importance 

 in the classification of these animals. The principal differences are 

 seen in the number of the incisors and molars. The usual number 

 of incisors is 4 in the upper, and 6 in the lower jaw. The 

 number is never in excess of this, though frequently falling 

 short of it. Thus, in some genera there are but 2 incisors above 

 and 4 below ; or there may be none above and but 2 below 

 When the number in the upper jaw is confined to 2 teeth the 

 central incisors are wanting. The number in the lower jaw is 



