370 THE VERTEBRATE SKELETON. 



have tuberculated crowns, and there are never less than two 

 pairs of incisors in the mandible ; often the incisors, canines, 

 and premolars are not clearly differentiated from one another, 

 and special carnassial teeth are never found. The cranial cavity 

 is small, and the facial part of the skull is generally much 

 developed ; often the zygomatic arch is incomplete. Clavicles 

 are well developed (except in Potamogale), and the hum ems 

 generally has an ent-epicondylar foramen. The femur fre- 

 quently has a ridge representing the third trochanter. There 

 are two suborders : 



Suborder (1). DERMOPTERA. 



This suborder includes only a very aberrant arboreal genus 

 Galeopitkecus, remarkable for its greatly elongated limb bones, 

 and peculiar dentition. The incisors of the lower jaw are 

 deeply pectinated or divided by several vertical fissures, the 

 canines and outer upper incisors have two roots. Ossified 

 intercentra occur in the thoraco-lumbar region of the vertebral 

 column. 



Suborder (2). INSECTIVORA VERA. 



This suborder includes all the ordinary Insectivora, such as 

 moles, shrews and hedgehogs. The upper and lower incisors 

 are conical, not pectinated. 



Order 8. CniROPTERA 1 . 



This order is perhaps the best marked and most easily 

 defined of all the orders of mammals. The anterior limbs 

 form true wings and the whole skeleton is modified in relation 

 to flight. 



The anterior limbs are vastly larger than the posterior ; 

 for all the bones except the carpals are much elongated, and 



1 See G. E. Dobson, Brit. Mm. Catalogue of Chiroptera, 1878. See 

 also other papers by the same author and by Oldfield Thomas. 



