FAUNA OF THE GOSATT FORMATION. 



629 



was long since appreciated by Mr. Hulke in describing his skull of 

 Iguanodon*. Therefore Bunzel's Avian and Crocodilian affinities of 

 the skull both fall to the ground, owing to this fundamental miscon- 

 ception of its characters. Hence it appears to me desirable to describe 

 the specimen anew, in order to render its structure clearer. The 

 specimen exhibits superior, lateral, inferior, posterior, anterior, and 

 cerebral aspects ; and on each of these I propose to offer a few remarks. 

 The fossil, as preserved, is 63 millim. broad behind, and 5 centim. 

 high, owing to the downward direction of the occipital condyle ; for, 

 although the skull obviously increases in height as it passes forward, 

 the height from the base to the fronto-parietal suture is only 4| 

 centim. The presphenoid bone is broken away ; but the length 

 from the fracture or suture to the back of the occipital condyle is 

 4| centim., and to the back of the supraoccipital bone is 5| centim. 

 Superiorly and externally the cranial region is moderately convex 

 from side to side, and also exhibits a slight convexity from front to 

 back (PI. XXVII. fig. 6), especially towards the outer borders, indi- 

 cative, I think, of the parietal bone just reaching the margin of the 

 temporal fosse on the right side. The surface of the bone is rough, 

 with slight and irregular close-set elevations, not so distinct as 

 those of a Trionyoc, but certainly suggesting the surface that is 

 sometimes seen when the scutes are removed from a Chelonian 

 carapace. There is also a transverse furrow running across the 

 bone, rather behind its middle, nearly parallel to the convex posterior 

 border, and therefore curving backward. The width of this superior 

 surface, as preserved, is nearly 5| centim.; but then the bone is 

 broken on both sides, though it has become thin and separated late- 

 rally from the brain-case. Its antero-posterior extent in the middle 

 line where greatest is just over 3 centim. I have no doubt that 

 the transverse groove (PI. XXVII. fig. 5) indicates the limit of the 

 parietal bone ; for the suture defining it is seen on the left side of the 

 cerebral surface and on the external lateral surface ; but I cannot 

 trace it across the upper surface, and it may be that the suture is 

 obliterated by ossification, consequent upon a scutal covering. The 

 groove recalls those which occur on the skulls of Lizards such as 

 Trachydosaurus, while the texture of the bone is not dissimilar ; and 

 hence it is also possible that we have here an explanation of the 

 absence of sutures, in the circumstance that they are covered up by 

 a layer of dermal ossifications. The parietal bone at the frontal 

 suture (PI. XXVII. fig. 6) is 9 millim. thick ; but at the transverse 

 groove the thickness is reduced to 7 millim., owing to cerebral exca- 

 vation beneath it. The area behind the groove terminates posteriorly 

 in a margin which is rounded, but suggests the idea that a plate 

 4 millim. thick in the middle, and becoming thinner laterally, was 

 superimposed upon the cranial bones. This region posterior to the 

 groove I suppose to be occupied by the supraoccipital bone. 



The posterior aspect of the skull is chiefly remarkable for the 

 elevated border above the foramen magnum, which was evidently 



* Hulke, Quart. Journ. Geol. Soc. vol. xxvii. p. 206. 



