BATS. 425 



they may be entirely wanting, or be present in the numbers of 

 1 — 1 to 2 — 2 in the upper, and from 1 — 1 to 3 — 3 in the lower 

 jaw ; they are always very small, and in the upper jaw commonly 

 unequal and separated by a wide median vacancy. Taking the 

 common simple-nosed Bat(l) {Vespertilio-murinus) as a type of the 

 Insectivorous group, we find its dental formula to be : — 



2—2 1—1 3—3 3—3 „„ 



m. — : c. — : pm. — : m. — : = oo. 



3—3 ' 1— 1 ' ■'^ 3—3 ' 3—3 



The first upper incisor (PL 112. fig. l,i.) has a slightly expanded 

 tri-dentate crown, separated by a basal ridge of enamel from a long, 

 slender, slightly curved, fusiform fang ; the second upper incisor 

 has a sub-bifid crown. The three lower incisors (i) are tri-den- 

 tate, and the crown of the outermost has an additional tubercle. 

 The crown of both upper and lower canines (c c) is sharp- 

 pointed, and its inner surface is indented by two grooves ; a basal 

 ridge divides it from the long conical fang. The first premolar is 

 very small, both above and below, and has a sharp-pointed simple 

 crown with a basal ridge, and a single fang ; the second premolar 

 is still smaller : both are soon shed. The third premolar, as it may be 

 called from its shape, though it has no deciduous predecessor, has a 

 triangular pointed crown, with a basal ridge, and is implanted above by- 

 three fangs ; in the lower jaw the crown is narrower, and is supported 

 by two fangs (p p). The first and second upper true molars (m), have 

 each a six-pointed crown supported by three fangs : the third molar 

 is compressed from before backwards ; its crown has three points or 

 tubercles, and is supported by three fangs. The first and second 

 true molars of the lower jaw have quinque-cuspid crowns, two of 

 the largest points being on the outer and three small ones on the 

 inner side, the crown is supported by two fangs ; the last molar 

 is the smallest, and is tri-cuspid. A well-developed ridge of enamel 

 surrounds the base of the crowm of each molar tooth both above and 

 below. 



(1) The insectivorous Cheiroptera are divisible into groups according to the modifications 

 of the tactile dermal appendages of the nose ; which may be wanting, as in the Vespertilio mur- 

 inus and other Leionycteridce ; or be present in the form of a simple leaf, as in the Vampire-bat 

 and other Phyllonyderidce ; or be developed into more complex forms, as in the Horse-shoe 

 Bat and other Lophonycteridee of Prof, de Blainville. 



