534 Professor E. BurclcharcU — On Hijperodapedon Gordoni. 



trying to effect a closer union of the Ebynchosaurians with Ehyncho- 

 oephalia vera. We ought rather to regard the former family as 

 a branch, in a wider sense, of the Ehynchocephalian stem, totally 

 independent of the true Ehynchocephalians, and linked in all 

 probability in a more direct manner to the lowest organized 

 Proterosaurid^. So long, therefore, as the inferior zygomatic arch 

 is held to be a differentiating character for the Ehynchocephalians^ 

 the Ebynchosaurians will have to be attached to them and not to 

 the Theromorpha. At the same time it should be borne in mind 

 that latterly Baur and Case have excluded Dimetrodon from the 

 Theromorpha, and have subsequently included it with the Ehyncho- 

 cephalians, chiefly on account of this character, and it is possible also 

 that a similar transfer awaits the Endothiodontidfe under similar 

 circumstances. It is to the latter that the Ebynchosaurians appear 

 to bear the greatest resemblance, but in this case also the resemblance 

 may be based upon analogy alone. 



The principal conclusions I have arrived at are as follows : — 



1. All the bones in the skull of Hyperodapedon Gordoni, as seen 

 in the specimen in the British Museum (apart from the occipital 

 region), can be identified, except such as may be still embedded 

 in the matrix. 



2. The upper side of the skull agrees with the one known for 

 Ehynchocephalians, with this difference, that the postorbital is 

 rather large and removed in position from the orbital. 



3. In the lower jaw five bones can be clearly distinguished, to 

 which an angular should be added, analogous to Bhynchosaunis. 



4. The maxillaries are edentulous ; the palatines possess numerous 

 rows of teeth in serial arrangement, which increase in size from 

 the front to the back. They are not changed, but their number 

 is augmented in their hinder margins ; their complete wear is 

 prevented by alteration in the position of the attritive surfaces. 

 The suture between the palate-bone and the maxillary lies to the 

 outside of the dentigerous portion, and is probably the same in the 

 Placodontia. 



5. Hyperodapedon, together with Rhynchosauriis, forms a separate 

 group of the Ehynchocephalians, viz. the Ebynchosaurians, which 

 are connected in a direct line with the lowest forms. This group 

 has no affinity with the Ehynchocephalians in a stricter sense ; 

 its analogies with the Chelonians, the Endothiodontidge, and the 

 ChampsosauridaB are physiological ones. 



Literature. 



1. Owen, R. — "Description of an Extinct Lacertian Reptile, Rhyncliosaurm 



articeps'" : Trans. Cambridge Phil. Soc, vol. vii (1842). 



2. Huxley, T.— I. Postscriptum to Sir Rod. Murcliisou, "On the Sandstones 



of Morayshire (Elgin, etc.) containing Reptilian Remains": Quart. Journ. 

 Geol. Soc, vol. XV (1859), p. 435. II. "On Sypcrodajoedon'' : ibid., 

 vol. XXV (1869), p. 138. III. " Further Observations upon Syperodapedom 

 Gordoni'' : vol. xliii (1887), p. 675. 



3. GiJxTHEK,, A.—" Contributions to the Anatomy of Hatteria'' : Phil. Trans.„ 



vol. clvii (1867). 



