THE OENITHOSCELIDA. 263 



step towards tlie bird. The pubes are not only as slender 

 and elongated as in tlie most typical bird, but tbey are 

 directed downwards and backwards parallel with the ischia, 

 thus leaving only a very narrow and elongated obturator 

 foramen, which is divided by the obturator process. 



It remains to be seen how far the hypsilophodont modi- 

 fication extended among the Ornithoscelida. The remains 

 of Compsognathus and of Stenopelyx tend to shew that it was 

 by no means universal. 



As to the hind limb, in existing reptiles : — 



1. The proximal end of the tibia has but a very small, or 

 quite rudimentary, cnemial crest, and it presents no ridge 

 for the fibula on its outer side. 



2. The flattened sides of the distal end of the tibia look, 

 the one directly forwards, or forwards and inwards ; and 

 the other backwards, or backwards and oiitwards. And 

 when the posterior edges of the two condyles of the 

 proximal end of the tibia rest on a flat surface which looks 

 forwards, the long axis of the distal end is either nearly 

 parallel with that surface, or is inclined obliquely from in 

 front and without, backwards and inwards. 



3. There is no depression on the anterior face of the tibia 

 for the reception of an ascending process of the astragalus. 



4. The distal end of the fibula is as large as, or larger 

 than, the proximal end, and articulates largely with a facet 

 on the outer part of the astragalus. 



5. The astragalus is not depressed and flattened from 

 above downwards, nor does it send a process upwards in 

 front of the tibia. 



6. The astragalus remains quite free from the tibia. 



In all these respects the leg of any existing bird (see 

 Fig. 78), is very strikingly contrasted with that of the reptile. 



1. The proximal end of the tibia is produced forwards and 

 outwards into an enormous cnemial crest, in all walking and 

 swimming birds (Fig. 78, A.) ; and, on the outer side, there 

 is a strong ridge for the fibula. 



2. When the posterior edges of the condyles of the tibia 

 rest iipon a flat surface, the one flat face of the distal end 



