MAMMALIA. 585 



have a well-developed pair of clavicles, bones which are 

 absent or vestigial in the latter order. Other generalised 

 features are the presence, in some, of ossified intervertebral 

 discs (see Mole), and of an episternum and the frequent 

 occurrence of an entepicondylar foramen and a third 

 trochanter. The placenta, like that of the Rodentia^ is 

 discoidal and deciduate. 



Many of the Insectivora are fossorial or arboreal, but 

 most are terrestrial. They are widely distributed throughout 

 the Arctogoean realm, but are absent from Neogoea and 

 Notogoea. In both these realms their place in nature is 

 occupied by insectivorous Polyprotodontia. 



SUB-ORDER I. — DERMOPTERA. 



The sub-order Dermoptera is constituted for the 

 remarkable so-called "flying-lemur" {Galeopithecus) of 

 the Malay Islands. It has a large patagium stretched 

 from the neck to the fore-limb, between the fingers laterally 

 to each hind-limb and thence to the tail. It is arboreal 

 and uses its patagium for "gliding" from tree to tree in 

 much the same way as Australian phalangers and the flying- 

 squirrels. 



Its structural peculiarities are chiefly as follows : — The 

 lower incisor teeth are deeply pectinated or cleft and the 

 second upper incisor and the canine have double roots, the 

 tibia and fibula are distinct, and there is an intertarsal joint 

 to allow of the hind-foot being rotated inwards for climbing. 

 The mammae are axillary. 



SUB-ORDER II. — INSECTIVORA VERA. 



The sub -order Insectivora Vera comprises the re- 

 mainder of the order, including the moles (Talpa) found 

 in the temperate parts of Eurasia, the hedgehogs {Erinaceus)^ 

 with great numbers of spines in addition, confined to 

 Europe, Asia and Africa, the shrews {Sorex) of the Hol- 

 arctic region, closely resembling mice in external appearance, 

 the tree-shrews {Tupaia) of the Oriental region and the 

 jumping-shrews {Macroscelides) of the Ethiopian region. In 

 all these five families the molar teeth are multi- or quadri- 

 tubercular, presenting a broad crown. The other four 



