Nodosaurus textilis Marsh. 125 



''The fragmentary skull of Stereocephalus Lambe does not 

 show generic distinctions from the present specimen [type of 

 Ankylosmirus magniventris Brown], as far as can be judged 

 from the figures and description, but it is much smaller, and 

 apparently the plates are not as synmietrical. It was found in 

 the Belly River beds of Canada, an earlier horizon than the Hell 

 Creek [Lance] beds, and is probably ancestral to Ankylosaurus." 



To what extent Brown will revise this opinion in the 

 light of his recently discovered ankylosanr material from 

 the Edmonton series, one can not say, nor is it possible 

 to compare Stereocephalus with Nodosaurus, as homol- 

 ogous elements are as yet unannounced. The same may 

 be said of Paleoscincus Leidy. 



Of the Old World forms, Polacanthus, with its very 

 perfect lumbar-hip carapace, is clearly the most sugges- 

 tive of Nodosaurus, possibly because of the fine preser- 

 vation of the most characteristic element, the pelvis. 

 The latter, seen from below, has been very useful in the 

 reconstruction and interpretation of that of Nodosaurus, 

 but the very perfection and extent of the armor, covering 

 as it does the entire posterior presacral and pelvic 

 regions, so that the outline of the ilia is scarcely percep- 

 tible, is a marked distinction from the condition of armor 

 development found in Nodosaurus. Polacanthus in this 

 regard is more suggestive of Stegopelta than of Nodo- 

 saurus. It is undoubtedly of the same lineage as the 

 American forms, but probably not directly ancestral to 

 Nodosaurus, unless there has been a secondary reduction 

 of the hip armature in the latter. 



Eeferences. 



Brown, Barnum. 1908. The Ankylosauridse, a new family of armored 



dinosaurs from the Upper Cretaceous. Bull. Amer. Mus. Nat. Hist., 



vol. 24, 187-201, figs. 1-20. 

 — 1917. Monoclonius, a Cretaceous horned dinosaur. Amer. Mus. Jour., 



17, 135-140, 4 pis. 

 Gilmore, C. W. 1914. Osteology of the armored Dinosauria in the United 



States National Museum, with special reference to the genus Stego- 



saurus. U. S. Nat. Mus., Bull. 89. 

 Hulke, J. W. 1881. Polacanthus foxii, a large undescribed dinosaur from 



the Wealden formation in the Isle of Wight. Philos. Trans. Eoy. Soc. 



London, 172, 653-662, pis. 70-76. 

 — 1887. Supplemental note on Polacanthus foxii, describing the dorsal 



shield and some parts of the endoskeleton, imperfectly known in 1881. 



Ibid., 187 B, 169-172, pis. 8, 9. 

 Lull, R. S. 1910. Stegosaurus ungulatus Marsh, recently mounted at the 



Peabody Museum of Yale University. This Journal (4), 30, 361-377, 



pi. 2, figs. 1-10. ' 



Lydekker, Richard. In Seeley 1892, p. 85. 



