150 Prof. H. G. Seeley on 



the process is about -^^ inch deep. The anterior process is 

 indistinctly defined, and was produced somewhat forward 

 to a point wliich was not in advance of the pubic process. 



The acetabulum is an arch with its anterior side inclined 

 forward at an angle of 45° ; the posterior side is shorter and 

 more vertical. The pubic process which forms the anterior 

 border is IfV iuch long and margins the front of the acetabu- 

 lum, with a long oblique ridge. 



The hinder border of the acetabulum is at first sharp, but 

 as it ascends it is reflected upward, so as to be flattened or 

 concave on the underside of the posterior process of the ilium. 

 The acetabulum is perforated by an arch which is similar in 

 contour to the external, outline of the acetabulum. This 

 specimen differs from that figured by Professor Huxley in 

 being smaller, in a more acute notch between the anterior 

 process of the ilium and the pubic process, in the much less 

 excavation of the notch between the pubic and ischiac pro- 

 cesses, in the relatively greater length of the pubic process 

 and of the anterior process of the ilium, which characters 

 may possibly be more than individual variation. 



Tiff. 3. 



Natural impression from the internal surface of the right ilium of a 

 species of Palceosaun/s. A caudal vertebra (c) in the same slab is 

 drawn posterior to the ilium. Brist. Mus. no. 63. -| nat. size. 



An example of a right ilium on slab 63, which shows the 

 internal aspect (fig. 3) , does not display any marks of attach- 

 ment to the vertebras, resembling in this Megalosaurs rather 

 than Crocodiles. It is as large as in an alligator about 10 feet 

 long. There is the same large development of the posterior 

 process of the ilium seen in all Triassic Saurischia, which is 

 also present in existing Crocodiles, but the margins of the 

 posterior process appear to approximate more rapidly, so as 

 to terminate in a rounded extremity. Only the crest of tlie 

 ilium is preserved, and this shows that the anterior angle was 

 reflected outward, making the bone concave in length. All 

 the lower portion of the ilium is indicated by a mould of the 



