moodie: armored cretaceous dinosaur. 261 



spines and excrescences it must have been a bizarre creature, 

 even in those Cretaceous days. 



The teeth (plate LVI, figs. 4 and 5) of Stegopelta are typi- 

 cally stegosaurian. There are a dozen of them in more or less 

 perfect state of preservation. They are all of practically the 

 same size and character, showing but little variation among 

 themselves. The crowns of the teeth, which measure 7 mm. in 

 breadth, are subcompressed and narrowly palmate with eight 

 radiating costae, all of which end at the tip in sharp points. 

 The roots of the teeth measure 15 mm. from the base of the 

 crown to the tip of the fang. In point of size and number of 

 costae the present teeth are so closely similar to those described 

 by Leidy (5) as a supposed lacertilian form, Paleoscincus, 

 that had the teeth only been found they would undoubtedly 

 have been referred to that genus. It is possible that Stegopelta 

 may eventually prove to be a Paleoscincus form. This, how- 

 ever, is hardly probable, on account of the great interval of 

 time separating the strata which have yielded the two speci- 

 mens, Paleoscincus occurring as it does near the top of the Fort 

 Pierre Cretaceous and Stegopelta near the top of the Fort Ben- 

 ton. Were the form one of a stable group this might not be 

 sound reasoning, but in a group of animals which evolved so 

 rapidly as did the dinosaurs one would hardly expect a genus to 

 continue for so long a time. At all events, the name Stegopelta 

 may be retained until more evidence is forthcoming concerning 

 Paleoscincus. If, as Hatcher believed (23), Lambe's Stereo- 

 cephalus is a Paleoscincus form, then Stegopelta is a good 

 genus, since it shows wide structural differences from the form 

 which Lambe has described. The tooth which Lambe (7) has 

 figured on page 57 certainly resembles those of Paleoscincus, 

 and if the tooth really is to be associated with the remains 

 described as Stereocephalus a question might arise as to 

 whether these remains were not in reality portions of the skele- 

 ton of Paleoscincus as Hatcher intimated. Lambe (8) says 

 the tooth provisionally associated with the Stereocephalus 

 remains "differs from those of the Red Deer river district, re- 

 ferred to the two species of Paleoscincus, and is about twice as 

 large as those of P. costatus." Just how it differs he does not 

 say, and one is at a loss in attempting to separate the forms 

 from his figures. Size alone is usually no safe criterion for the 

 separation of animal forms, and more particularly genera. I 



