658 S. W. WILLISTON 
the water. The entire absence of a neck, which is characteristic 
of all the lower vertebrates of the Texas Permian, the large, ungainly 
but flattened head, the short body and tail, and short, rather stout 
limbs, all must have given to the creature a very bizarre aspect. . 
The distinction of Tvrematops from other genera of the rhachito- 
mous amphibians described from Texas seems certain. Its relationship 
with Eryops is evident, but, aside from its smaller size and greater 
slenderness, the structure of the head separates them widely. From 
Acheloma, which IJ at first thought might be the same, there seem to be 
marked differences. Cope’s description of Acheloma leaves certain 
parts in doubt, parts of much importance in the discrimination of 
the two genera, especially the size and shape of the vacuities. He 
describes the premaxillary teeth as five in number and of large size, 
whereas in Tvematops they are six in number and are among the 
smallest of the whole series. He also states that the humerus of 
Acheloma, a very remarkable thing for an amphibian, has an entepi- 
condylar foramen, whereas there is no trace of such in the present 
form. Dr. Matthew of the American Museum has very kindly 
compared the type of Acheloma, at my request, and confirms these. 
details, and also informs me that the skull is different in shape from 
the figure sent him of Tvematops. 1 have no hesitation, hence, in 
giving to the present specimen the generic name Tvematops, chosen in 
reference to the numerous vacuities of the upper side of the skull. 
A further discussion of the habits and relationships of Trematops 
and Eryops will be given in a future paper, after other forms have been 
described, especially a nearly perfect skeleton, with all its bones in 
natural relations, of a small species of Pariotichus, which will furnish 
the subject for the next paper of this series. 
