34 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 77 



the width of this process in the type of Palaeosincus rugosidmis; 

 likewise the articular distal end is much smaller. 



There are some remnants of the palate present but a description 

 of these would add nothing of interest. 



The lateral temporal fenestra opens outward and backward be- 

 tween the quadrate and the enveloping armor. 



Beneath and somew^hat posterior to the orbit on either side is a 

 large scute whose strongly developed keel is directed downward and 

 outward. Its anterior outer border is acutely edged and rounded off 

 from the front toward the back. This process completely hides the 

 articulation of the lower jaw with the quadrate, and furnishes it with 

 ample protection. 



The orbits are suboval in outline, with a diameter anteropos- 

 teriorly of 76 millimeters and dorso-ventrally about 30 millimeters. 



The skull is widest across the orbits and much constricted trans- 

 versely in front, a feature that will at once distinguish Dyoplosaurus 

 from Euoplocephalus and Ankylosaurus. 



Measurements of tJie skull 



Mm. 



Greatest length (estimated) median line 365 



Greatest breadth across center of orbits 325 



Greatest breadth immediately posterior to nares 175 



Teeth. — There are five teeth preserved, one in the center of the 

 right maxillary and the crowns of four others found in the dirt near 

 the skull. Since there were no other animal remains with this speci- 

 men, there can be no doubt of the association. As the lower jaw 

 was entirely missing it may be inferred that all of these teeth belong 

 in the upper or maxillary series. The teeth are alike in form and 

 size. Their very small size appears to be distinctive, a fact that can 

 not be attributed to their being germ teeth as shown by one much 

 worn tooth which has the same proportions as the unworn. Each 

 consists of a laterally compressed crown with a long cylindrical root. 

 The crowns measure 4.7 mm. antero-posteriorly, 4 mm. transversely 

 through the cingulum, and about 5 mm. in height. The crown at 

 the base has a swollen cingulum that is especially pronounced on 

 the outer side. The edges of the teeth are denticulate, there being 

 nine or ten denticles on each tooth, four and five respectively on either 

 side of the apical one which is decidedly posterior to the central ver- 

 tical line as shown in Figure 18. On the outer side the crown is 

 divided into five principal columns by vertical fluting (see fig. 18B) 

 which subsides on the internal side before reaching the cingulum. 

 The three larger denticles are transversely flattened with acute edges, 

 the others presenting more or less rounded points. The teeth are 

 worn on the inner side showing that the lower teeth bite inside the 



