488 MANUAL OF ZOOLOGY. 



and characterised by the fact that the four outer or ulnar 

 fingers are greatly developed and elongated, and are united 

 together by a leathery flying-membrane or " patagium," which 

 is continued from the hand and arm to the side of the body 

 and hind-limb. By means of this patagium the Bats possess 

 the power of flight. Clavicles are always present. The teeth 

 vary a good deal, but there are always canines. The placenta 

 is deciduate and discoidal. 



Order XII. Insectivora, comprising the Moles, Shrew-mice, 

 and Hedgehogs, characterised by having the crowns of the 

 molar teeth furnished with sharp and pointed cusps. Well- 

 developed clavicles are present in almost all cases. The pla- 

 centa is deciduate and discoidal. 



Order XIII. Quadrumana, comprising the Lemurs, Apes, 

 and Monkeys. Dentition usually the same as in man, or with 

 an additional prsemolar on each side of each jaw, or varying a 

 good deal in the lower forms. The series of teeth is uneven 

 and interrupted. The innermost digit of the fore-limb (pollex) 

 is opposable to the other fingers when present, but it may be 

 wanting. The hallux is also opposable to the other toes of the 

 hind-limb, so that the hind-feet constitute prehensile hands. 

 Clavicles are always present. The placenta is deciduate and 

 discoidal. 



Order XIV. Bimana. This order includes Man alone. The 

 dental formula is 



22 I I 22 33 



The teeth are nearly even, and are not interrupted by any 

 interval (diastema). The pollex or thumb on the fore-limb is 

 opposable to the other digits, but this is not the case with the 

 hallux or great-toe. The attitude of the body in progression 

 is habitually erect. The placenta is deciduate and discoidal. 



