Chapter III. 



A DESCRIPTION OF CHENOPROSOPUS MILLERI, GEN. ET SP. NOV. 



By Maurice G. Mehl. 



The specimen herein described was discovered by Mr. Paul C. Miller, of the 

 University of Chicago expedition, in 191 1, on Poleo Creek, in the vicinity of Arroyo 

 de Agua, northern New Mexico. It was found alaout 50 feet away from and ap- 

 proximately 2 feet below the skeleton of Ophiacodon Marsh described by Williston 

 and Case in the following pages. The horizon is almost identical with that of the 

 type specimens of Ophiacodon and Sphenacodon Marsh, collected by Mr. David 

 Baldwin in 1878. The illustrations in this chapter were drawn by the author. 



Fig. 4. — Skull of Chenoprosopus milleri, X yi- A, lateral view; B, dorsal view. 



The material on which this genus and species is based consists of an incom- 

 plete skull. The anterior third and the left side, to the median line, are complete, 

 with the exception of the loss of the upper posterior border of the skull, a little 

 of the quadrato-jugal region, and a small portion about and including the left 

 naris. Fragments from the right side were obtained, but they are so badly crushed 

 and so incomplete that they are of little use other than in determining the position 

 of the teeth. The specimen was inclosed in a hard sandstone matrix which, for 

 the most part, was freed from the bone quite readily, leaving many of the sutures 

 distinct and the pitting undisturbed. The skull is somewhat distorted and sHghtly 

 compressed laterally. This distortion has cracked the surface and this, with the 

 rather thorough ossification, has made the determination of some of the sutures 

 extremely difficult. Only those that can be determined with certainty are shown 

 in full lines, while the others are indicated by dots. 



