MONOTREMES. 103 



by horny projections or " cornules." There are 19 dorse-lumbar 

 vertebrae, well-marked sternal ribs, and a pair of large marsupial 

 bones placed on the pelvis. 



The two genera of the Order differ in many important respects, 

 especially in the shape of the skull. Ornithorhynchus has a 

 broad, flat rostrum, forked in front, which supports the beak, and 

 in which first the teeth and then the cornules are implanted; 

 while in Echidna the snout is long, narrow, and toothless, and 

 forms merely a long tube for the lodgment of the tongue, as in 

 the true Anteaters (Myrmecophagd). In the recently discovered 

 Proechidna bruijnii from New Guinea, of which a fine skeleton is 

 mounted, the snout is nearly twice as long as the brain-case, and 

 very much curved downwards, while in the common Echidna it is 

 much shorter and curved upwards. 



In both Ornithorhynchus and Echidna the anterior limbs are 

 more powerfully developed than the posterior, the humerus espe- 

 cially being exceedingly thick, and provided with large ridges for 

 the attachment of muscles, reminding us of a similar development 

 in moles and other digging mammals. 



