56 ' MR. E. LYDEKKEK ON A NEW 



since all otter described limb-bones are solid, I am inclined to . 

 think that tbis hollow may be due to post-mortem decay. This 

 bone is distinguished from the humerus of Cetiosaunis oxoniensis, 

 by its more slender form and the greater prominence of the deltoid 

 crest ; and in the latter respect, so far as I can see from the small- 

 sized figures published by Prof. Marsh, accords more nearly with 

 the homologous bone of Brontosaurus. The question then arises 

 whether this form may not be generically identical with Ornithopsis, 

 in which case, in strict right of priority, that name should yield 

 place to the older Pelorosaurus. It should be observed that Mantell 

 identified with Pelorosaurus the caudal vertebrae which we may 

 regard as the types of Cetiosaurus hrevis of Sir R. Owen ; and I 

 observe, in a recent note, that Prof. Seeley * now not only accepts 

 this identification, but regards both forms as belonging to Ornith- 

 opsis. The occurrence of the remains of both Pelorosaurus and 

 Cetiosaurus hrevis in the Sussex area is, so far as it goes, in favour 

 of their belonging to one and the same form ; but since anterior caudal 

 vertebrge of the latter occur (as I shaU mention immediately) in the 

 Isle of Wight, I do not think much stress can be laid upon this point, 

 one way or the other. On Professor Seeley's view all the remains 

 of large Wealden Sauropoda (excepting Thecospondylus and Titano- 

 saurus) will be referable to Ornithopsis \ but the British Museum 

 possesses cervical vertebrae t, from the Isle of Wight, which are 

 greatly longer than those of OrnitJioj)sis SulJcei, and in this respect 

 are much more like those of the American Morosaurus ; and as I 

 shall show that the latter appears to be the Transatlantic represen- 

 tative of Cetiosaurus, there is a considerable probability that these 

 specimens may be referable to C. hrevis. The anterior caudal 

 vertebrae of the latter difi'er, moreover, from those of Brontosaurus 

 (the ally of Ornitlioims) by the absence of distinct postzygapophyses, 

 by the broad angulated faces of their centra, and their articulation 

 by two facets with the open chevrons. A series of associated spe- 

 cimens in the British Museum, from Brook (j^os. 36559, 28640), 

 belonging to C. hrevis, and comprising the last lumbar vertebra, the 

 sacrum, and an anterior caudal vertebra, also aff'ords evidence tend- 

 ing in the same direction. Thus the last lumbar vertebra has small 

 lateral pits, but is otherwise solid, while the sacrum consists of 

 four haemaUy flattened vertebrae, solid throughout, as in the sacrum 

 of Morosaurus t ; that of Brontosaurus being, on the other hand, 

 completely hollowed. These specimens are, moreover, much too 

 small to have belonged to OrnifJiopsis ; while in the Pox Collection 

 there is the imperfect right half of a vertebral centrum (I^o. E. 209) 

 of the latter, which I regard as belonging to the last of the lumbar 

 series, and which is much larger than the last lumbar of the pre- 

 ceding specimen, and diff'ers by the more extensive lateral pits, and 

 the complete honeycombing of the body of the centrum. Again, I 

 find part of the centrum of a trunk-vertebra from the Wealden of 

 Sussex diflPering considerably from the dorsals of 0. HuXkei. So 



* Geol. Mag. 1887, p. 479. t Nos. E,. 96 and 46780. 



X See Mai'sh, " Classification of Dinosauria," in Eep. Brit. Assoc, for 1884. 



