﻿230 ALLEN S NATURALISTS LIBRARY. 



found abundantly in the Secondary rocks of South Africa, and 

 which are known as Anomodonts ; the Reptiles in question 

 being the only known Vertebrates having a shoulder-girdle of 

 the type characterising the Monotremes. Assuming these 

 Anomodonts to be more or less nearly related to the ancestors 

 of the latter, we are, however, still quite in the dark as to the 

 intermediate links ; as we are also in regard to the genetic 

 relationship of the Monotremes to what we may term the 

 True Mammals. There occur, however, in the Secondary and 

 Tertiary rocks of many parts of the world certain very remark- 

 .able extinct Mammals which from the peculiar characters of 

 their molar teeth are termed Multituberculata. Now these 

 teeth present a certain distant resemblance to those of the 

 Duck-bill among the Monotremes, and this, together with 

 certain other evidence, may be indicative of some relationship 

 between the two groups. The relationship must, however, at 

 best, be but distant, and since the majority even of these 

 ancient Multituberculates appear to have been comparatively 

 specialised animals, it will be evident that we are still a very 

 long way oif the discovery of the true phylogeny of the Mono- 

 tremes. 



It may be added that in the Duck-bill the temperature of 

 the blood is some 20*^ F. lo\\er than in ordinary Mammals. 



THE DUCK-BILLS. FA^IILY ORNITHO- 

 RHYNCHID^. 



Aquatic fluviatile Monotremes, in which the sexes differ 

 markedly in size, presenting the following characters : 



Muzzle in the shape of a broad, flattened beak, covered with 

 delicate and sensitive skin, assuming in the dried state a horny 

 consistence; tongue not extensile; fur without spines; tail 

 well-developed, broad and flattened ; feet modified into swim- 

 ming organs, with the toes broadly webbed, and the soles 



