304 ANNALS NEW YORK ACADEMY OF SCIENCES 



they bear to the American Permian reptiles from Texas and New Mexico. 

 One of the largest and best-known animals is called Pareiasaurus. It is 

 a large-limbed reptile, about nine feet in length and standing about threq 

 and one-half feet in height. In many points of its organization it shows 

 affinities with the American reptile Diadectes, of which a mounted skele- 

 ton is to be seen in the American Museum, Another group of animals 

 contemporaneous with Pareiasaurus is the reptilian group of Dinocepha- 

 lians. These also were large reptiles with very powerful limbs. Although 

 herbivorous and having no remarkable specialization of the spines of the 

 vertebrae, they are nevertheless fairly closely allied to the very remarkable 

 American fin-backed Pelycosaurs, of which skeletons are to be seen in the 

 American Museum. 



One of the most striking peculiarities of the Karroo reptiles is that 

 almost all agree with Pareiasaurus and the Dinocephalians in having 

 powerfully developed limbs. How these have been evolved is a matter of 

 doubt, but there can be little question that it was this strengthening and 

 lengthening of the limbs that started the evolution which ultimately re- 

 sulted in the formation of the warm-blooded mammals. 



The best-known, and in some respects the most remarkable, of the 

 Karroo reptiles belong to a group named by Owen the Anomodonts, from 

 their having horny beaks like the turtles or birds with, in addition in 

 many forms, a pair of large walrus-like tusks. The first specimen was 

 discovered as far back as 1844 and was called Dicynodon, but, although 

 many skulls have been discovered, only three or four fairly good skeletons 

 have been found. In limbs, shoulder and pelvic girdles and essential 

 structure of the skull and in the number of joints of the toes, they strik- 

 ingly resemble the mammals, and although the curious development of 

 the beak obscures the mammal-like character of the skull, it is essentially 

 built on the mammalian plan, and there is little doubt that although the 

 Anomodonts are a side offshoot from the mammalian stem, they are 

 closely allied to the mammalian ancestor. 



A form nearly allied to Dicynodon is called Endothiodon. It has no 

 large tusk but a number of small teeth. Although much rarer than 

 Dicynodon, fortunately an almost complete skeleton has been discovered, 

 which has recently been mounted in the Museum laboratories by Mr. 

 Charles Falkenbach under my direction, and of which a photograph is 

 given. The extremely mammal-like condition of the limbs is very mani- 

 fest, and there is little doubt that the animal waddled about somewhat 

 after the manner of the pigmy hippopotami of Liberia, seen at the New 

 York Zoological Park. Attention may be called to the relatively enor- 

 mous size of the skull and the curious way in which the long point of the 

 lower jaw passes up into the groove in the upper. 



