[STERNBERG] PANOPLOSAURUS MIRUS 95 



are well developed and set well apart on the six cervicals seen. The 

 diapophyses are well developed and resemble those of the axis. 

 (Plate I, Fig. 1, d). 



The dorsal vertebrae are very similar to those of Ankylosaurus 

 magniventrus, as far as seen, though none have ribs ankylosed'^ to them. 



The ilium was supported by no fewer than six vertebrae, of which 

 the anterior five are firmly coalesced (Plate I, Figure 2). Four of 

 these are regarded as true salerais and of the remaining two one is 

 probably a modified dorsal vertebra and the other a caudal vertebra. 



The centrum of the dorso-sacral has weathered away but the 

 neural arch and left rib are present. The neural arch and spine are 

 firmly coalesced with the first sacral. To the diapophysis is co- 

 ossified a long, slender rib, the distal end of which lies on the distal 

 end of the first sacral rib and gives support to the ilium. 



The centra of the four sacral vertebrae are firmly coalesced, all 

 trace of separation being obliterated. The neural arches and spines 

 are also firmly united, except the neural spine of number four, which 

 is free above the zygapophyses. 



The centra are very much modified, the anterior ones being 

 merely abroad, thick plate, almost flat on the inferior surface and 

 concave superiorly. Posteriorly they narrow transversely, thicken, 

 and become more convex inferiorly, making the shape of the posterior 

 centrum more nearly that of a normal centrum. 



In Panoplosaurus true sacrais have been developed through the 

 modification of caudal vertebrae to a greater extent than in Stego- 

 saurus^ and to a less extent than in Polacanthus^ . Two true sacrais 

 have been added in this way to the primitive number which, according 

 to Hatcher^", has been found to be two in the case of the Dinosaurs. 



The sacral ribs are stout, horizontal processes, broadly expanded 

 at the ends and are composed of the true sacral ribs and the diapo- 

 physial laminae thoroughly coalesced throughout. The three anterior 

 ones spring each from two vertebrae and are broadly expanded and 

 thoroughly co-ossified at their distal extremities. The sacral rib of 

 the fourth vertebra differs from the others only in that it springs 

 from one vertebra only and is not united with the others distally. 

 The first two are much stouter throughout than the succeeding ones. 



^ The Ankylosauridae a New Family of Armored Dinosaurs from the Upper 

 Cretaceous, by Barnum Brown. Bull. Amer. Mus. Nat. Hist., vol. XXIV, 1908, 

 p. 194, Fig. 12. 



8 Gilmore, U.S. National Museum, Bull. 89, 1914, pp. 54, 55, Figs. 22, 23. 



9 Hulke, Phil. Trans. Roy. Soc, vol. 178 B, 1887, pi. 9. 

 !« Carnegie, Mus. Mem., vol. I, 1901, p. 32. 



