THE SK ULL OF BRA CHA UCHENIUS— WILLISTON. 479 



maxillary processes already described. Each bone is overlapped in 

 part in front by the tongue-like processes of the maxilla, and I can not 

 be sure whether any part of it reaches the nareal border, though I 

 think not. Near the posterior extremity of tliis tongue there is a very 

 distinct suture, extending backward and a little outward for a short 

 distance, thence nearly directly backward to a point above the upper- 

 most part of the orbit; on the left side the bone has been separated 

 at tliis suture. Posteriorly, on the outer side, the bone joins the 

 postorbital for a short distance obliquely; the suture then turns 

 inward to join the parietal transversely. The bone is long, pointed 

 anteriorly, flattened or gently concave above in its middle, united on 

 its inner side in front with the premaxilla, beliind with the rostrum of 

 the parietal, posteriorly with the postfrontal and postorbital, on the 

 outer side with the prefrontal. It is of course possible that the bone, 

 as described, is composed of two elements, the most anterior of which 

 would be the nasal, but of such division there is no evidence in this 

 specimen. (See Plate XXXVII, /r.? rmf.) 



Prefrontals. — The prefrontals are rather broad, irregularly shaped 

 bones, forming the whole of the antero-superior border of the orbits 

 and the posterior inferior margins of the nares. The inner border of 

 each bone, as already described, joins the frontal throughout. 

 Posteriorly, for a short distance, it joins the postorbital, differing in 

 this respect from the prefrontals of Trinacromerum. Its orbital 

 border is thin and arched, terminating at the extreme front angle of 

 the orbit. Below, the bone joins the lachrymal by a short suture run- 

 ning forward and outward in continuation of the line of the orbital 

 margin to the maxillary suture, which has been described. Ante- 

 riorly the bone is emarginated by the hind border of the nareal open- 

 ing, the tongue of the maxilla, as described, overlapping it and conceal- 

 ing its extent. The bones are convex and smooth, each pierced by two 

 small foramina. On the left side the bone, while not crushed or 

 distorted, has been separated from the adjoining bones and forced 

 upward somewhat. Inasmuch as its shape and extent on tliis side 

 agree quite with those of the opposite side, as determined from the 

 sutures, there can be no doubt of its relations and form. There is no 

 indication on either side of a sutural division. 



Parietals. — The parietal foramen is an elongated opening, oval in 

 shape and about 40 mm. in length. In front of the foramen, the 

 parietals appear to continue forward as an elongated, narrow rostrum, 

 to disappear under the facial extremity of the premaxillne, divided in 

 the middle by a distinct suture from a little in front of the foramen. 

 The surface on either side of this mesial suture is plane or concave, 

 presenting a number of distinct longitudinal ridges and grooves, wliich 

 begin near or on the sides of the foramen. The greatest width of these 

 prolongations is at the hind end, where they together measure 50 mm. 

 Proc. N. M. vol. xxxii— 07 31 



