488 Professor R. Burckhardt — Oa Hijperodcqjedou Gordoni. 



asserted by that author, who also gives the number in Spjienodon as 

 twenty-five. Apart from this, the entire pelvic region appears to 

 me to be scarcely well enough preserved to positively assign to it 

 two sacral vertebrae. 



Whether the above inference was possible from the first specimen 

 at Huxley's disposal, or not, I do not know, as he does not express 

 himself on this point in his first description of this portion of the 

 skeleton of Hyperodapedon in Quart. Journ. GeoL Soc, 1859, vol. xv, 

 p. 460. From analogy in Sphenodon, Huxley has estimated the 

 length of its tail to be about 110 mm., though no reliable data are 

 obtainable from the fossil itself. I would also wish to remark here 

 that the sacral vertebrae are only f the length of the hindmost 

 thoracic vertebrae, and from this fact alone it may be seen that 

 Huxley's computation of the length of the tail appears to be an 

 over-estimate. 



Of the remaining portions, the shoulder - girdle alone calls for 

 some remarks here. The position assigned by Huxley to the inter- 

 clavicle is the correct one, but there is an error as regards the 

 spatulate shape of its posterior margin which requires modification. 

 Posteriorly the episternum terminates in quill - like processes, 

 separated from each other by a deep incision, as is the case in a great 

 number of Lacertilians. Besides this, but noticeable only on the 

 right side, its clavicular margin bifurcates into two pointed pro- 

 jections, as in BhyncTiosaurus. The bone which Huxley designated 

 the coracoid is really composed of two parts, the coracoid and the 

 praecoracoid. 



The most important part of this fossil is its skull, and it is here 

 principally that I dissent from Huxley's interpretations. I therefore 

 felt compelled to refigure and re-describe it, a proceeding to which 

 I shall add also those inferences which I have been enabled to draw 

 from other fragmentary specimens deposited in the British Museum 

 (Natural History). 



The general topography of the skull has been admirably rendered 

 by Huxley. As a further adjunct to his admission that, although 

 Hyperodapedon was essentially terrestrial in habits, yet it had at the 

 same time a predilection for leading an aquatic life, may be mentioned 

 the anomalous position of the orbits, which are so strangely directed 

 upward and situated forward as to deserve to be specially pointed 

 out here. 



The first attempt towards a more precise knowledge of the com- 

 ponent parts of the skull than that by Huxley was by Dr. A. Smith 

 Woodward, who partly traced the boundaries of the nasals, the 

 postorbitals, the jugular and other bones. It has been a great 

 satisfaction to me, as the result of my endeavours to make out the 

 sutures, to find myself so entirely in accord with Dr. Smith Woodward, 

 without any deviations whatever, the more so as I did not consult 

 his sketch at the time. Numerous fresh details having come to 

 light, during a more protracted study of the fossil, a fresh illustra- 

 tion of the skull cannot be dispensed with under the circumstances. 

 I have therefore executed the accompanying drawings from photo- 

 graphs taken by myself. 



