MONOTREMATA. 



59 



the Golden Moles (Chrysochloris] (See woodcut, p. 25), the third 

 and fourth digits bearing large digging claws, while those of the 

 other three are small and slender. 



Order XII. MONOTREMATA. 



(Case 98.) 



The Order Monotremata, like the Marsupialia, represents by 

 itself one of the primary sections or subclasses into which the 

 Mammals are divided. In all their anatomical characters these 

 animals show a remarkably low type of organization, a type trans- 

 mitted more or less directly from some of the earliest Mammalian 

 forms. 



Fig. 24. 



Echidna acukata. 



The Monotremes lay eggs and have pouches, but their mode of 

 incubation is not yet satisfactorily known ; they are without true 

 mammary nipples, the mother's milk exuding from groups of pores in 

 the skin. The males are provided with remarkable horny spurs on 

 their heels, connected with a small gland on the back of the thigh, 

 the function of which is entirely unknown. The temperature of 

 the blood is lower than that of other mammals, recent observations 

 having shown that that of Echidna stands only at about 78, 

 some 20 lower than that of man, and about 30 below that of 

 the average of birds. 



The few living species of Monotremata are referred to two 

 families^ the first being the Echidnida:, characterized by the long 



