AET. 16 FOSSIL KEPTILES FROM MONTANA GILMOEE 3 



Tyfe locality.— '&QC. 16, T. 37 N., R. 8 W., Milk Eiver, Blackfeet 

 Indian Eeservation, Glacier County, Montana. 



Horizon. — Two Medicine formation. Upper Cretaceous. 



The specimen on which the present description is based was found 

 on the north side of Milk River about one-half mile west and south 

 from the locality where the type of Brax^hyceratops montanensis '' 

 was discovered by the writer in 1914. All the bones were disarticu- 

 lated and widely scattered, but it was quite apparent they pertained 

 to a single individual as there was no duplication of parts. 



Shull. — The skull, aside from slight flattening due to postmortem 

 crushing, is in an almost perfect state of preservation. Normally 

 depressed, it diminishes in both height and breadth toward the muz- 

 zle, which is squarely truncate. Widest immediately posterior to the 

 orbits, the breadth abruptly contracts behind the eyes, forming a 

 distinct notch on either side as contrasted with those of much lesser 

 degree in both Panoplosamms mirus and Edmontonia longiceps. 

 The orbits are of moderate size and set far back. The narial open- 

 ings are large and open outward and upward. The lateral temporal 

 fenestra look outward and slightly backward. 



The whole of the exposed skull surface, top, front, and sides, is 

 covered by a few ossified dermal plates. These are coossified with 

 the underlying skull bones, concealing them from view. The plates 

 are defined by shallow circumscribing sulci, which in this specimen 

 can not be traced out in their entirety, as is shown in Plate 2. 



In so far as the number, form, and proportions of these head 

 plates can be determined, they most nearly resemble those of Edmon- 

 tonia longiceps. The observed difference in form and proportions 

 between the plates of Palaeoscincus 7'ugosidens and those of E. 

 longiceps and Panoplosaurus mirus, in all probability are of but 

 little anatomical significance, for in dermal bones there seems to be 

 considerable variation among individuals of the same species. 



Viewed from the side the superior outline of the skull is moderately 

 convex from front to back and likewise from side to side. Behind 

 the line of the orbits on either side of the midline are large shallow 

 depressions as in the cranium of E. longiceps. The withdrawal 

 inward of the dentigerous border of the maxillary, brings about a 

 depressed buccal area of considerable extent, well illustrated in Fig- 

 ure 2. Dermal ossifications cover the entire side of the skull, thus 

 obliterating all sutures between the individual bones. 



In the posterior view (fig. 1) the skull bones are free from dermal 

 covering and although the individual elements can be determined, all 

 of the sutures are coalesced thus rendering it impossible to determine 

 their precise limits. 



sGilmore, C. W., Prof. Paper, 103, U. S. Geol. Surv., 1917. 



