PROF. H. (;. SEKLEY ON SAURODESMUS ROBERTSONI. 109 



towards a generalized Lacertilian type, in so far as the characters 

 are not Crocodilian, which is especially shown in the compressed 

 distal radial margin. 



The Trias of Elgin has already yielded Telerpeton^ Ilyperodapedon^ 

 and Staf/onolepis, and the fossil is well distinguished from these. 

 It is somewhat smaller than Nyperodapedon, which has the proximal 

 end of the bone greatly expanded and concave, though less expanded 

 than in IStagonoUpis, but in neither genus is there the same resem- 

 blance to a Crocodilian type which is seen in the fossil under review. 

 Among the extinct Orders it is in some ally of the Ornithosaurs 

 that an approximation to the Linksfield type might be expected, for 

 it is only in the hnmerus of the Pterodactylia that a close general 

 resemblance to the fossil is found in those distal characters in which 

 it varies from Crocodiles. 



As preserved, the bone is ^'2 cm. long, and when perfect may have 

 been from 1 to 2 cm. longer. At the fracture it is 3*5 cm. wide, 

 and the bone is 1 cm. thick in the middle, where a muscular impres- 

 sion marks the large angle made with the ulnar and radial sides of 

 the head. The middle of the shaft, which is nearly cylindrical, is 

 1*1 cm. wide. The distal end is 3'2 cm. wide. The articulation 

 ascends the snperior surface a little on two moderate ridges with a 

 concavity between them. It is about 1'5 cm. thick on the ulnar 

 side, and thinner on the radial side, the two parts being defined by 

 the anterior and posterior concavities. These differ from the corre- 

 sponding constrictions in the humerus of Crocodiles in that the 

 depression in front is much narrower, while the inferior concavity is 

 much wider. The form of the distal articulation indicates, I think, 

 that the bones of the forearm were placed as in Crocodiles, and not 

 as in Lizards or Anomodonts. 



The compressed ulnar margin (supposing it to be unbroken), with 

 a muscular attachment at its edge, would constitute an ordinal 

 difference from existing reptiles. The fossil, if grouped with the 

 Crocodilia, belongs to a suborder hitherto unknown, and defined by 

 a combination of Crocodilian and Lacertilian characters which is not 

 Saurischian. 



Discussion on the above two Papers. 



Mr. Lydekker agreed with the Author in regarding the Australian 

 tibia as that of a Dinosaur, but asked how it was geuerically distin- 

 guished from Dimodnsaarus or Massosjoondf/lus. He was glad that 

 the Author termed the bone from Elgin a somewhat unsatisfactory 

 specimen ; in the speaker's opinion it was not worthy of being made 

 the type of a genus. He differed from the Author in regarding the 

 bone as being solid, and expressed his belief that although it might 

 belong to a Rhynchocephalian or an extremely generalized Chelonian, 

 it was certainly not Crocodilian, in any accepted sense of that term. 

 He further enquired the Authors meaning in using the expression 

 *' Lacertihan affinities " in an apparently loose way. He concluded 

 by protesting against the use of the term "Saurischia" for the typical 

 Dinosauria. It was perfectly permissible to divide the Dinosauria 



