﻿WEALDEN FORMATIONS. 



5 



in Iguana it includes, with the same bones, also a part of the premaxillary ; in Crocodilus 

 proper it is wholly surrounded by the pterygoids ; in Teleosaicrus the palatines combine 

 with the pterygoids to complete it anteriorly. 



With regard to the opening answering to the hinder nostril in Teleosaurus, we find 

 in Varanus that the halves of the divided vomer also contribute to bound or form the pointed 

 anterior prolongation of the vacuity, 1 in the formation of which, as the pterygoids take 

 the most constant and always the chief share in Lacertilia and Chelonia, and as the 

 vacuity so bounded does not in these reptiles serve as the hinder or palatal opening of the 

 nostrils, the term ' interpterygoid ' appeared to me to be most conveniently applicable. 



In the skull of the Varanus niloticus figured by Cuvier 2 the presphenoid is prolonged 

 so as to seem to divide the c interpterygoid vacuity ' into a pair ; the point of the bone, 

 however, in nature inclines upward, and does not join anteriorly either the palatine or 

 vomerine bones. In the larger monitor {Varanus indicus) and in Iguana the presphenoid 

 (PI. II, figs. 6 and 7, 9) has a like relation to the interpterygoid vacuity (ib., «), but is not 

 so far produced. 



Von Meyer, in his figure of the base of the skull of Belodon Kapffi? represents the 

 interpterygoid vacuity as divided by a longitudinal production, apparently, of the 

 pterygoids, the lateral parts or plates of which form with the palatines the outer border 

 of such vacuity. The homologues of the ' pterygo-maxillary vacuities ' are much reduced 

 in size, are external and posterior to the ' interpterygoid ' openings, and are exclusively 

 formed by the pterygoid and ectopterygoid, which, uniting externally to those openings 

 as well as internally, are interposed betw r een the maxillary and the ' pterygo-maxillary 

 vacuity/ Von Meyer, as usual, puts no figures or letters of reference upon the bones 

 and orifices, nor refers thereto by means of such symbols in his text. 



Assuming, however, that the usually careful and accurate delineator of fossil 

 specimens has correctly represented the palatal characters of his Belodon Kapffi, it 

 offers the nearest resemblance to the characters of that part of the skull of 

 Hylaochampsa. 



In the proportion of this part of the skeleton of the Wealden Crocodile transmitted to 

 me by Mr. Fox an extent of three inches of the hinder part of the bony palate is preserved 

 (PI. II, fig. 25). In this extent four vacuities are more or less completely shown ; they 

 are in two pairs. Of the medial pair (PI. II, fig. 25, «, «) the left is entire, and the 

 right lacks but a small part of its antero-external border ; of the lateral pair (ib., y, y) the 

 left wants a part of its antero-external border ; but of the right, only a small part of the 

 inner and hinder border is preserved. 



The left pterygoid (24) is entire in its relations to the above vacuities, only the postero- 

 lateral branch (answering to a, figs. 6 and 7) being broken off. The external branch 

 (figs. 25, 0, 7, c), extends as usual, outward and forward to articulate with the ectopterygoid 



1 Cuvier, torn, cit., pi. xvi, fig. 3, &c. &c. 2 Ib., ib. 



3 ' Palreontographica,' zehnter Band, pi. xxxix, p. 227 (18G3). 



