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 Rodenfra, is 
discoidal and deciduate. 
Many of the Jmsectivora are fossorial or arboreal, but 
most are terrestrial They are widely distributed throughout 
the Arctogoean realm, but are absent from Neogcea and 
Notogeea. 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 mamme are axillary. 
SUB-ORDER II.--INSECTIVORA VERA. 
The sub-order Jnsectivora Vera comprises the re- 
mainder of the order, including the moles (Za/a) found 
in the temperate parts of Eurasia, the hedgehogs (Z7inaceus), 
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 (Zupaia) of the Oriental region and the 
jumping-shrews (AMacroscelides) of the Ethiopian region. In 
all these five families the molar teeth are multi- or quadri- 
tubercular, presenting a broad crown. The other four 
