io8 



SKULL OF ECHIDNA 



CHAP. 



affairs. It must be remembered, however, that the Cetacea 

 show the same characters, though it is possible that they too 

 are developed from a low mammalian stock. In the vertebral 

 column we find the typical mammalian seven cervicals ; but 

 those characteristically mammalian structures the epiphyses are 



oc.cond 



Fio. 51. Ventral view of skull of Echidna aculeata, and right half of mandible, any, 

 Angle of mandible ; aud.oss, auditory ossicles ; cond, condyle of mandible ; cor, 

 coronoid process ; max, maxilla ; oc.cond, occipital condyle ; pal, palatine ; p.max, 

 premaxilla ; pt, pterygoid ; sq, squamosal ; ty, tympanic ring. (After Parker and 

 Has well.) 



totally absent in Echidna, and only to be seen in the tail-region 

 in Ornitliorliynchus. In having only the capitular head to the 

 ribs, these mammals are evidently far removed from all other 

 mammals, and are even more reptilian than the Theromorphous 

 reptiles. The large clavicles and the interclavicle (Fig. 52, 



