AND SAUROPTERYGIANS OF THE PURBECK ETC. 39 



tioned specimens belong to one and the same individual. The 

 type ilium is fortunately the left one, and is therefore strictly 

 comparable with the type of I. Daivsoni. This specimen, although 

 it has been fractured, is nearly entire, but unfortunately the pre- 

 acetabular process is broken, and a fragment is missing near its 

 origin, so that its exact length cannot be determined. The ex- 

 tremity of the pubic process is also missing. Compared with the 

 ilium of /. Dawsoni (fig. 1 B), this specimen appears to indicate a 

 somewhat smaller form, and is of a relatively deeper type, with a 

 highly convex superior border, a more concave external surface, 

 and a less defined acetabulum and ischial tuberosity. The pre- 

 acetabular process is deeper and apparenily shorter, and has no 

 roof-like inner extension at its origin from the preacetabular notch, 

 nor any tendency to an outward inclination of its inferior border. 

 Posteriorly the difference from /. Daiusoni is still more decidedly 

 marked. Thus the lateral surface of the postacetabular portion 

 terminates in a comparatively sharp point ; while inferiorly this 

 portion gives off a shelf-like projection standing out almost at right 

 angles to the vertical plate. As minor features of this ilium, it 

 may be observed that the preacetabular notch is very shallow from 

 above downwards, the prepubic process is deflected downwards, 

 the interval between the pre- and postacetabular notches is compa- 

 ratively short, and in the preacetabular notch the surface of the 

 bone is rounded off. The vertical height of this specimen from the 

 inferior border of the middle of the acetabulum is llS inches, and 

 the approximate total length (allowing one inch for the missing 

 fragment of the preacetabular process) 32 inches. 



The associated ischium has the hammer-shaped head character- 

 istic of the one I have figured in association with the ilium of /. 

 Bavjsoni in my previous paper. 



The sacrum, which is imperfect, is characterized by the lateral 

 compression of the component vertebree, and thereby agrees with 

 the somewhat smaller sacrum from the Weald Ch),y referred, and I 

 believe rightly, by 8ir R. Owen to /. ManteUi. The vertebral 

 centra are completely anchylosed together. 



That the present form, as typified by the ilium, is perfectly distinct 

 from /. bernissartensis and I. MantelVi of the Upper Wealden is quite 

 evident ; the great development of the inwardly directed horizontal 

 shelf of the postacetabular portion of the ilium being of itself a 

 sufficient distinction. The vertebrae from the Upper AVealden on 

 which Sphenosjwndylus gracilis is founded appear to be much too 

 small to have belonged to this form ; while since its distinctness 

 from /. Dawsoni has been already sufficiently indicated, there ap- 

 pears no doubt as to the right of Ljaaaodon Fittoni to rank as a 

 distinct species. 



In referring this species to the genus Ljuanodon rather than to 

 the allied Cmnptosaurus {Camptonotus) I have been mainly guided 

 by the characters of the sacral vertebra?, which are those of one of 

 tne typical group of Ljuanodon^ and also by the largo size of tlio 

 present species — Camptosaurus being typically of comparatively 



