[lambe] PANOPLOSAURUS M I RUS 47 



The third plate preserved, presumably the third of the series, is 

 represented by the right half only and indicates a plate which, when 

 complete, was like those in front except that it was considerably 

 shorter. Its exterior border is imperfect, but the full breadth of the 

 plate was apparently much the same as that of the other two. The 

 union of the two halves does not appear to have been fully complete. 



These broad plates with low keels and a deep groove in the-.mid- 

 line evidently followed each other in a longitudinal series on the neck 

 from close behind the skull, but how many plates there were in 

 the series and how far back the series extended is left for future dis- 

 coveries to reveal. 



SktUl (Plates I, II, III, and IV). The skull of Panoplosaurus is 

 depressed, and diminishes in breadth and height toward the front 

 where it ends squarely, the outline as seen from above being nearly 

 triangular, and in lateral aspect sub-ovate. The orbits are small 

 and placed very far back. The narial openings are also rather 

 small and open outward at the anterior end. 



The whole of the exposed surface of thehead, above, in front, and 

 on the sides, consists of ossified plates covering and concealing the 

 underlying bones of the cranium and mandible. On the under sur- 

 face, between the mandibular rami, there is a close aggregation of small 

 bony scutes and smaller ossifications. 



The most prominent features of the skull of Panoplosaurus and 

 those that arrest the attention on first viewing it are its breadth in 

 comparison with its length; its compactness and breadth of surface 

 curvature ; the large size of most of its covering plates ; the squareness 

 of the muzzle; the posterior position of the orbit and the consequent 

 recession of the lateral temporal fossa; the flatness and breadth of the 

 lower surface of the mandibular rami ; the withdrawal inward of the 

 dentiguous border of the maxillary and dentary bones, causing a 

 depressed buccal area of considerable extent; the presence in this area 

 of a large cheek-plate, and in the nostril of small plates; and the di- 

 rection of the occipital condyle which faces downward and slightly- 

 backward. 



Dimensions of Skull of Type of Panoplosaurus. 



mm. 



Maximum breadth behind orbits 294 



Anterior breadth, in advance of external nares 121 



Length, in a straight line, from occipital condyle to middle of 

 anterior end (upper border of mouth opening) 355 



