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Show 1891.] BRITISH REMAINS OF HOMOXOSAURUS. 169 classification of the Rhynchocephalia, Lydekker ' and Zittel2, the former has overrated the importance of these characters in assigning to Homceosaurus and allies the rank of a suborder, opposed to Sphenodon, Rhynchosaurus, and Hyperodapedon; while the latter has underrated their importance in uniting Homceosaurus and Sphenodon in one and the same family. Homceosaurus deserves to stand as the type of a distinct family, in the immediate neighbourhood of the Hatteriidce, to which it is more nearly related than to the Rhyncho-sauridce or than are the latter to the Hatteriidce. The classifications of the two authors above referred to differ as follows:- 1. LYDEKKER. fFam. Homaiosauridce. ' Subord. Homoeosanria \ „ Pleurosauridce. f ,, Telerpetidce. Subord. Sphenodontina 1 " J, , n l .,' Ord. Rhynchocephalia [ „ Rhynchosauridce. Ord. Proterosauria ,, Proterosauridce. Champsosaurus is not mentioned, but forms a third Suborder (Sinicedosauria) of the Rhynchocephalia in the author's more recent Manual3. 2. ZlTTEL. , Subord. Rhynchocephalia s. s. j F a m ' ^no^ntid^ J r [ „ tthynctiosauridce. Ord. I ( „ Proterosauridce. Rhynchocephalia 1 Subord. Proganosauria -! „ Mesosauridce. I_ [ „ Champsosauridce. Both these arrangements appear to me unsatisfactory. The Proterosauria are allowed ordinal rank by Lydekker merely provisionally and " in deference to the views of Prof. Seeley." But his definition of the Order is not diagnostic, for such characters as " Cervical vertebrae much elongated" and " Posterior caudal vertebrae with divided neural spines " can certainly not be meant to characterize an Order. As to the latter character in particular, I have to remark that it occurs in certain Lacertilia, and is particularly marked in a genus which, one would think, might not have escaped notice. I now exhibit a skeleton of Lacerta ocellata, with the object of showing the curious division of the neural spine of some of the caudal vertebrae (fig. 2, p. 170) into an anterior and a posterior part, as believed to be characteristic of the Proterosauria. In the specimen exhibited, the caudal vertebras, from the 9th to the 19th inclusively (the rest of the tail being regenerated), bear two neural spines, the anterior directed obliquely forwards, the posterior directed obliquely backwards. Both are processes of the posterior moiety of the vertebra (the caudal vertebrae of these and other fragile-tailed Lizards being divided into two), thus showing that the division of the spine has 1 Cat. Foss. Rept. i. p. 290 (1888). 2 Handb. Pal. iii. p. 583 (1889). 3 Nicholson and Lydekker, Man. Pal. ii. (1889). |