On the Affinity between the Dinosauria n Reptiles and Birds, 69 



which are imbedded by single fangs, and apparently lodged in distinct 

 alveoli. The summit of the crown, when unworn, is sharp and pre- 

 sents no trace of the serrations characteristic of Iguanodon ; but it H 

 sinnated by the terminations of the strong ridges of enamel w T hich 

 traverse the outer surface of the crown. The teeth thus present 

 some resemblance to those of Iguanodon; but the author regarded the 

 two forms as perfectly distinct, and named the species under con- 

 sideration HypsUophodon Foxii. Of the lower jaw the right ramus 

 is present ; but its distal extremity is broken off, and its teeth are 

 concealed. On the outer surface of the lower jaw the centrum of a 

 vertebra is preserved. 



The author then referred to a fossil skeleton in the British Mu- 

 seum, which has been regarded as that of a young Iguanodon ; it 

 is from the same bed as the skull previously described. The author 

 remarked that, in form and proportions, the vertebrae were quite 

 different from those of Iguanodon, and apparently identical with 

 those of his new genus, as shown by the centrum preserved with the 

 skull : the animal had at least four well-developed toes ; and other 

 peculiarities were indicated, which seem to prove that it was quite 

 distinct from Iguanodon. This skeleton the author identified with 

 his Ilypsilopliodon Foxii, and described its characters in detail, 

 dwelling especially upon the peculiarities of the pelvic bones, which 

 are singularly avian in their structure. 



4. " Further Evidence of the Affinity between the Dinosaurian 

 Reptiles and Birds." By Professor Huxley, F.R.S., President. 



In this paper the author reviewed the evidence already cited by 

 himself and others (especially Professor E. D. Cope) in favour of 

 the ornithic affinities presented by the Dinosauria, and discussed at 

 length the recently ascertained facts which bear upon this question, 

 some of the most important of which are derived from the species 

 described by him in the preceding paper under the name of Ilyp- 

 silopliodon Foxii. He summed up his paper by a comparison of the 

 different elements of the pelvic arch and hind limb in the ordinary 

 reptiles, the Dinosauria and Birds, and maintained that the structure 

 of the pelvic bones (especially the form and arrangement of the ischium 

 and pubis), the relation between the distal ends of the tibia and the 

 astragalus (which is perfectly ornithic), and the strong cnemial crest 

 of the tibia and the direction of its twist furnish additional and im- 

 portant evidence of the affinities between the Dinosauria and Bird?. 



Mr. Seeley doubted whether these animals should be called 

 lleptiles at all, as they seemed to him to form a group distinct alike 

 from reptiles, birds, and mammals, but occupying an intermediate 

 position. In the hinder limbs of Fterodactylus the analogies were 

 closer with mammals than with birds. He thought it possible that 

 the peculiar structure of the hinder limbs of the Dinosauria was 

 due to the functions they performed rather than to any actual 

 affinity with birds. 



The President, in reply, stated that HypsUophodon, from the 



