194 



PORTHEUS MOLOSSUS, Cope. 

 Proceedings of the American Philosophical Society for 1871, p. 173. 



Represented by four individuals: one from Fox Canon, near Fort Wal- 

 lace, with complete cranium, and many vertebras and radii ; a second from 

 another part of the same, with large part of cranium ; and a third and fourth 

 from Lower Butte Creek bluffs, both with fragments of cranium and other 

 portions. In the first specimen, the jaws are perfect and dentition complete. 



The premaxillary is vertically oval, convex externally, nearly flat within, 

 and more than half underlaid by an anterior lamina of the maxillary. The 

 anterior or median margin is regularly convex, and exhibits no surface or 

 suture for union with the bone of the opposite side. Its posterior margin 

 extends obliquely backward to beneath the superior articular condyle of 

 the maxillary, and has a ragged edge, though the suture is squamosal. Its 

 superior margin is deeply inflected in front of the condyle, and then convex 

 and thickened. The anterior margin is thick and rugose with tubercular 

 exostoses. There are but two teeth, which are very large, and directed 

 obliquely forward ; the first is two-thirds the diameter of the second. 



The maxillary is a large laminiform bone, with the upper margin consid- 

 erably thickened proximally, but much thinned distally. It is abruptly con- 

 tracted at the distal two-thirds its length, apparently for the attachment of a 

 supernumerary bone. The extremity is curved saber-shape upward, and has 

 an acute toothless edge. The teeth are four small, five large, and eighteen 

 small. These teeth, except the largest, have cylindric bases; the crowns 

 (and bases of the latter) are slightly compressed or oval ; they are straight 

 and regular, and lean backward. The middle one of the five is largest, being 

 six times as long as the small ones, but little more than half as long as the 

 large premaxillary or mandibular. The surface of the maxillary is rugose 

 with small tubercles on its lower half, and has shallow grooves for nutritious 

 vessels running downward and forward. 



The mandibular rami are short and deep, and have but little mutual 

 attachment at the symphysis. They are not incurved at that point, and were 

 bound by ligament only. There is no coronoid bone, and the articular is dis- 

 tinct. It is short, of a rather irregular wedge-shape, and supports half the 

 cotylus, above which it sends a short acuminate process. The angular has a 

 prominent angle, like half an ellipse, somewhat contracted at the base ; below 



