596 



CHEIROPTERA. 



.Fig. 281. 



the occipital foramen, in others not so. The 

 occipital crest is triangular, stronger in the 

 insectivorous than in the frugivorous form. 

 In many there is also a longitudinal crest. 

 The face is broad. The orbits are not com- 

 plete in either group, and the temporal fossa 

 is large, but the zygoma in many very slender ; 

 in some it is horizontal, in others slightly 

 convex above. The nasal opening is very 

 considerable ; and in many whole genera, as 

 in Rhinolopfius, in Plecotus, and several others, 

 in consequence of the intermaxillary bones not 

 meeting each other, it is not closed at the 

 lower part. In the genus Pteropus, and some 

 others, as is seen in fg. 282, 283, though the 

 intermaxillary bones meet in front, yet, as the 

 arch is very small and narrow from before 

 backwards, the palatine foramina unite and 

 form a single large opening. 



From the extreme thinness of the cranial 

 bones, the internal surface corresponds exactly 

 with the external, and there is no vestige of 

 a bony tentorium, which is so strong in many 

 of the Carnivora. 



The frontal bone in the genus Pteropus 

 presents a prominent orbitar process ; it re- 

 sembles that of Man, and of the Quadrumunu, 

 in the circumstance of the two portions be- 

 coming early united. The parietals, also, 

 unlike those of the examples just named, form 

 but a single bone. 



The temporal bone has a very extensive 

 development of its acoustic portion ; a cha- 

 racter which is of the utmost importance to 

 their peculiar habits, as the organ of hearing 



Fig. 282. 



Fig. 283. 



requires to be extensive in those animals which 

 prey by night, and especially in such as feed 

 upon insects and pursue them on the wing. 



The occipital bone is remarkable from the 

 narrowness of its body, the transverse direction 

 of the condyles, the short, thin, and convex 

 form of its squamous portion, and particularly 

 from the unparalleled proportionate size of the 

 occipital foramen, which is nearly vertical and 

 rounded. 



Fig. 284. 



Fig. 285. 



Cranium i>f 



Cranium of Phyllostoma. 



The jugal bone is small in most of the bats 

 and very strait. 



The superior maxillary bone is considerably 

 elongated in this order, particularly in. the 

 frugivorous genera. The difference in this 

 respect which exists between the frugivorous 

 and insectivorous forms is shewn in the cranium 

 of a Pteropus belonging to the former (Jig. 

 281, 282, 283), and a Phyllostoma to the 

 latter group (Jig. 284, 285, 286). In the 

 former case, the portion occupied by the teeth 

 fully equals in length the portion of the cranium 

 posterior to it ; in the latter it is little more 

 than as two to three. The number of teeth con- 

 tained in this bone varies considerably. There 

 is, however, always a single canine tooth on 

 each side, which is tolerably robust and sharp. 

 The molares of the insectivorous Bats are 

 always shorter than those of the frugivorous, 

 and are furnished with sharp points, the latter 

 being truncated and longitudinally grooved. 

 They vary in number from , to f, or 5. 



The intermaxillary bones are always very small 

 and short ; they contain small incisores, varying 

 in number according to the genera, from two 

 to four in the upper, and in the lower jaw from 

 two to six, there being always either the same 

 numberin the two jaws, or two more in the lower 

 than in the upper; thus there is always one 

 of the following formula;! \\$. The articu- 

 lation of the lower jaw is transverse. The 

 ascending ramus, with its coronoid process, is 

 large and strong, rising very high above the 

 level of the condyle. 



The vertebral column. The cervical verte- 

 bra; are in general very little raised, but they 

 are developed laterally, so as to present the 

 broadest portion of the whole vertebral column, 



