OS PUBIS OF POL.ICANTHUS FOXII. 85 



Polacanthus Foxii, and shows that the Wealden fauna contained more 

 than one type of heavily-armoured Saurian. 



It is not improbable that the dermal bone figured ^ from Gosau, 

 which was referred to Cratceomus, and compared in form to the 

 horn core of an ox, may be the horn upon the frontal bone. If so, 

 it establishes a striking difference between that genus and StrutJiio- 

 saurus, which has a small skull, without anything to indicate supra- 

 orbital horns such as Lave been suggested for Cratceomus. Cope 

 has compared it to Monoclonius or the horn of Agatliaumus,^ and 

 Marsh to the horn of Triceratops.^ On this comparison Zittel ^ 

 has placed Cratceomus in the suggested sub-order Ceratopsia. The 

 bone may possibly be a link of alliance between Aguthawnus and 

 Cratceomus. But I do not discover evidence of stronger affinity 

 between those genera than is manifest between Cratceomus and 

 Polacanlhiis, or between Polacanthus and Omosaurus. So that t 

 am led to associate all those genera in near alliance, in the 

 Seelidosaurian division of the order Ornithischia. 



[Sote. — The pubis of PolacantJius has been freed from the matrix 

 by Mr. Eichard Hall, since this paper was read. — December 31, 



1891.] 



Discussion. 



Mr. Lydekker said there Av^as no doubt that the bone in question 

 was an imperfect left pubis of Polacanthus ; and it was important as 

 confirming the relationship of that and the allied genera to the 

 Iguanodonts. 



He agreed with the Author in considering that the present dis- 

 tinctness of the ilium on the under surface of the shield of Pola- 

 canthus in the British Museum had only recently appeared, and was 

 probably due to more complete desiccation. He remarked that the 

 ilium beiug situated internally to the ribs was a character found 

 elsewhere only in adult tortoises, and that it was probably due to 

 the impact of the shield on the ribs rendering it impossible for 

 another bono to grow between the two. 



The speaker was glad to hear that the Author was convinced 

 of the close alliance between the AmericsLn Agathaumus {Triceratops) 

 and Struthiosaurus {Cratcvomus) of the Austrian Cretaceous, an 

 alliance which he himself had already indicated in his ' Palaeon- 

 tology. ' All this confirmed his view as to the close affinity be- 

 tween all the Dinosaurs of N. America and Europe. 



^ Op. cit. pi. xxviii. fig. 4. 



^ E. D. Cope suggested this identification to me in 1886. 

 3 Geol. Mag. for 1889, p. 207; ibid, for 1891, p. 193. 

 * ' Handb. der Palaeoutol.' Band iii. Abtb. i. p. 753. 



