THE SKULLS OF ARAEOSCELIS AND CASEA, 
PERMIAN REPTILES 
S. W. WILLISTON 
University of Chicago 
There are few Permian reptiles of greater interest at the present 
time than the peculiar one I briefly described in this journal! 
three years ago as Araeoscelis gracilis. At the time of the descrip- 
tion the material in the University collections had not been prepared, 
and it was in the hope of acquiring additional material from the 
Craddock bone-bed near Seymour, Texas, whence the type speci- 
mens came, that I have delayed the publication of further details 
concerning the genus. Unfortunately the bone-bed seems to be 
exhausted, at least so far as Araeoscelis is concerned. The material 
of the University has now been worked up thoroughly by Mr. 
Miller, and is sufficient to reveal nearly all the details of the skeletal 
structure of this strange reptile, which in many ways departs widely 
from all other known reptiles of the Texas deposits. The object 
of the present paper is to describe briefly the structure of the skull 
for the information of others working on allied material. The 
full description of the skeleton, with illustrations, will be published 
later. 
The skull, as shown in the accompanying figures, will not require 
a detailed description at this time. Suffice it to say that the struc- 
ture of the temporal region is determined positively, save perhaps 
the precise union of the squamosal and jugal. The absence or 
vestigial condition of the lacrimal I am also confident about. The 
skull in life may have been slightly narrower than is shown in the 
figure; I do not think it could have been wider. 
It has been suggested, especially by Huene, that Avaeoscelis 
shows affinities with the lizards. The structure of the skull con- 
firms this suggestion in a startling way. Really about all that 
seems necessary to convert Araeoscelis from a “theromorph”’ into 
a primitive squamate reptile is the reduction of the squamosal from 
t Journal of Geology, XVIII, 587, October, 1910. 
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