494 CHORDATA. 
body, covered not only with thick fur but with strong 
pointed spines scattered amongst the hair. The general 
colour is brownish and the spines are usually yellowish. 
The facial part of the head is produced into a long tubular 
rostrum. The eyes aresmall. The limbs each have five 
toes and in the typical species all are clawed. The tongue 
is long and protrusible. There is a small poison-spur on 
the hind-limb. The tail is almost absent. The animal is 
fossorial and anteating in its habits and can burrow rapidly. 
It is said not to make a nest but to carry its egg, which 
has a thin horny shell, in a temporary pouch. The mam- 
mary glands are like those of Ornithorhynchus. The skull 
Fig. 339.—SKULL OF ORNITHORHYNCHUS x 3. 
Maxilla. -% 
Intermaxillary. Ag — Symphysis. 
Horny Pad. 
Condyle. 
Foramen Magnum. 
A, Ventral view of skull. B, The mandibles from above. 
of Echidna, in its modifications for ant-diet, is rather like 
that of the true anteaters. We may note (1) the absence of 
teeth ; (2) the great elongation of the facial region; (3) the 
degeneration of the lower jaw or mandible. The functions 
of teeth and lower jaw have largely been usurped by a long 
adhesive tongue. 
OrnerR IIl.—AUlotheria. 
These consist of a series of small extinct mammals 
(Plagiaulax, Microlestes), chiefly known to us by their 
mandibles or lower jaws and their teeth. They occur in the 
