Genus Lysorophus, Cope. 239 



Doubtless Williston is right in regarding Lysorophus as a 

 mud-borrowing animal, and many of its specialisations are 

 due to this habit, such as the greatly elongated snake-like 

 body with very numerous vertebrae, great reduction of the 

 limbs, relatively small size of skull, loss of the arches, and 

 advanced position of the quadrate. And the somewhat 

 similar chai'acters, acquired by convergence in other groups 

 which have similar habits, have given rise to some striking 

 superficial resemblances to Lysorophus in the Gymnophiona, 

 the Amphisbsenans, and the Typhlopidse. 



But, apart from all modifications in Lysorophus due to a 

 burrowing habit, the skull is undoubtedly fundamentally an 

 Amphibian skull, and the only known Amphibia, recent or 

 extinct, with which it seems at all allied are the Urodela, 

 and, more remotely, the Anura and the Gymnophiona. 



Note by Prof. W. J. Sollas. 



Some years ago Dr. Broom obtained, through the kindness 

 of Dr. Matthew, two specimens of Lysorophus, and these he 

 presented to me for investigation by serial sections; at the 

 same time he made a most generous a Idition to this gift by 

 placing in my hands, to dispose of as I thought fit, a paper 

 embodying the important conclusions to which he had been 

 led from his study of the specimens in American museums. 



My own study is now completed, and I hope soon to give 

 a full and exact account of the structure of the skull in all 

 its details. This wilt confirm all the more important con- 

 clusions of Dr. Broom, and in justice to him I can no longer 

 withhold from publication the paper which he entrusted to 

 me in 1914. 



One or two minor emendations ought, perhaps, to be 

 made. Thus, the vacuity between the vomers, as it is repre- 

 sented in fig. 1, does not really exist; these bones are 

 without thickened margins and meet in the middle line ; 

 and, again, the articulare of the lower jaw is a comparatively 

 large and important bone. 



On the other hand, there can be no doubt that the cranial 

 walls include, as Dr. Broom suggests, a large " sphen- 

 ethmoid " and " alisphenoids." These are shown in section 

 in the accompanying figures (figs. 4 & 5). 



The whole anatomy of the skull recalls in a striking 

 manner that of Siren or Menopomus, and to my mind Lyso- 

 rophus is without doubt an ancestral Urodele. It presents 

 some remarkably interesting primitive characters. 



