634 



PEOE. H. Gr. SEELEY ON THE KEPTILE 



than has hitherto been suspected *; and it may well be that different 

 genera present modifications which affiliate representatives of the 

 group towards Crocodiles on the one hand and birds on the other. 

 But I cannot believe that any order, however homogeneous, could 

 have spanned the interval between the Crocodile and the bird, 

 though there can be no doubt that this skull of Struthiosaurus makes 

 a nearer approach towards the bird than does the skull of any living 

 reptile ; its differences from the bird-skull are precisely those which 

 distinguish it from the Crocodile, little as we know or can infer con- 

 cerning the suspensory arches for the lower jaw. In the base of the 

 skull not being covered with pterygoids there is a notable difference 

 from Crocodiles of the surviving type ; but then the base of the skull 

 is not bird-like, any more than it is like that of any other animal. 

 It is one of the most distinctive points of the Dinosaurian skeleton. 



It would be desirable to compare this specimen with other Cretaceous 

 genera ; but, with the exception of Acanthopliolis, none of these have, 

 as yet, yielded any evidence of the brain-case. One fragment, found at 

 Folkestone at the base of the Chalk with the remains of the Acantho- 

 pholis horridus, is briefly referred to by Prof. Huxley ; and on in- 

 spection it proves, though clearly allied, to belong to a different genus, 

 a fact that will be best demonstrated by a description of the specimen 

 and comparison of the figures (PI. XXVII. figs. 6 & 8 and 5 & 7). 



Note on the Base oe the Skull oe Acanthopliolis horridus, Huxley. 



Professor Huxley's account of the skull of Acanthopliolis is so 

 brief that it would be difficult to be sure from it of the identity of 

 the specimen, especially since Prof. Huxley describes characters 

 which we are now unable to recognize, though it is, of course, 

 possible that the specimen is in a less perfect condition than when 

 originally noticed. I therefore reproduce Prof. Huxley's original 

 remarks (Geol. Mag. 1867, vol. iv., Huxley on Acanthopholis horridus, 

 p. 66). 



" Of the skull I possess only a very much mutilated fragment, 

 showing the basioccipital and basisphenoid. The occipital condyle 

 measures 1*4 transversely, or has about the same diameter as that 

 of the skull of a Crocodilus hiporcatus which measures 16 inches in 

 length from snout to occiput. But it is more elongated transversely 

 and excavated above than in the Crocodile, and the exoccipitals 

 enter more largely into its composition. The Crocodilian disposi- 

 tion of the Eustachian tubes is absent ; and the carotids run up the 

 side of the basisphenoid in Lacertilian fashion. The sella turcica has 

 a well-developed posterior plate." 



This fragment (PI. XXVII. figs. 7 & 8) comprises the base of the skull, 

 and includes the basioccipital and basisphenoid, which are completely 

 ankylosed, and give no indication whatever of suture. I am similarly 

 unable to detect any sutural evidence of the exoccipital; nor can I re- 

 cognize the basioccipital condyle, which I believe to have been directed 



* Professor Marsh, since this was written, has published a classification of 

 American Dinosaurs (Amer. Journ. Sc. vol. xxi. p. 423). 



