Principal Forms of the Dinosauria. 327 



All the known members of the group appear to have had an 

 osseous dermal armor, more or less complete. 



One of the best preserved specimens of the Stegosauria in 

 Europe was described by Owen, in 1875, as Omosaurus arma- 

 tus, and the type specimen is in the British Museum. It is 

 from the Kimmeridge Clay (Upper Jurassic), of Swindon, 

 England. The skull is wanting, but the more important parts 

 of the skeleton are preserved. Various portions of the skele- 

 ton of several other individuals have also been found in Eng- 

 land, but the skull and teeth still remain unknown. 



A recent examination of these specimens by the author dis- 

 closed no characters of sufficient importance to separate them 

 from the genus Stegosaurus, and, as the name Omosaurus is 

 preoccupied, they should, for the present, at least, be referred 

 to Stegosaurus. The discovery of the skull and the dermal 

 armor may not unlikely prove them to be distinct, but the 

 parts now available for comparison do not alone authorize their 

 separation. 



The type specimen of Anthodon serrarius, Owen, a frag- 

 ment of a jaw from South Africa, and now in the British 

 Museum, has teeth so very similar to the American forms of 

 Stegosaurus, that, judging from these alone, it would naturally 

 be referred to that genus. Hylmosaurus, Mantell, from the 

 Wealden, has teeth of the same general type, but most of those 

 referred to it, by Mantell and others, pertain to the Sauropoda. 

 This genus, as well as Polacanthus, Hulke, from the same 

 formation, Acanthopholis, Huxley, from the Cretaceous, and 

 Scelidosaurus, Owen, from the Lias, are known from English 

 specimens, but have not yet been found on the continent. No 

 American forms of these genera have yet been discovered. 



An interesting Cretaceous member of this group is the 

 Struthiosaurus, Bunzel, 1871, apparently identical with Danu- 

 hiosaurus of the same author, 1871, and Cratmomus, Seeley, 

 1881. It is from the Gosau formation of Austria. Although 

 only fragments of the skeleton and dermal armor are known, 

 some of these are very characteristic. One specimen of the 

 latter, figured by Seeley, and regarded as a dermal plate, bear- 

 ing a horn-like spine " exactly like the horn-core of an ox,"* 

 is very similar in form to some problematical fossils from 

 America, the exact horizon of which is in doubt. f 



* Quarterly Journal of the Geological Society of London, vol. xxxvii, Plate 

 XXVIII. fig. 4, 1881. 



f Additional remains secured during the past season prove conclusively that 

 some of these "horn-cores," if nut all, were attached to the skull in pairs, and 

 one specimen found in place has since been described by the author as Ceratops 

 montanus (This Journal, vol. xxxvi, p. 477. December, 1888). It is from the 

 Laramie formation of Montana. Others have been found in Colorado and in 

 Wyoming. These are all much larger than the European specimens. 



