574 Correspondence — Messrs. Bristoiv and Whitaker. 



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 discusses at 

 length the recently ascertained facts w^hich 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 Hyp- 

 silophodon 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 enemial crest 

 of the tibia and the direction of its twist, furnish additional and 

 important evidence of the affinities between the Dinosauria and 

 Birds. 



Discussion. — Sir Roderick Murchison, who had taten the Chair, inquired as to 

 the habits of the HypsilopJiodon. 



Mr. Hulke mentioned that Mr. Fox had two blocks containing remains of a large 

 portion of the Hypdlophodon, all procured from a thin bund of sandstone near 

 Cowleaze Chine. On one the pelvis is almost entire, as well as the right femur, 

 the tibia, which is longer than the femur, four long metatarsal bones, and an 

 astragalus. All the long bones are hollow. Portions of at least eight individuals 

 have been found in the same bed. 



Mr. Seeley doubted whether these animals should be called Reptiles 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 Pierodaetylus the 

 analogies were closer witb 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 Bypsilophodon, from the character of its teeth, 

 probably subsisted on hard vegetable food. He expressed a hope that Mr. Fox would 

 allow a closer examination of his specimens to be made. He was unable to agree 

 with Mr. Seeley's views. He was inclined to think that the progress of knowledge 

 tended rather to break down the lines of demarcation between groups supposed to be 

 distinct than to authorize the creation of fresh divisions. 



coK-ie-ESiPoivriDiEi^oiB. 



THE CHESIL BANE. 



Sir, — The letter of Colonel Greenwood " On the Formation of 

 the Chesil Bank," in the last number of the Geological Magazine, 

 is so discursive, and takes up so many points not immediately 

 treated of in our ^ paper on the subject, that it is somewhat difficult 

 to answer briefly. 



As far as we can gather, the two chief objects Col. Greenwood has 

 in view are : — Istly, to complain that we have appropriated the 

 term " natural groin " used by him in reference to Portland, and to 

 which he reserves the exclusive right; and, 2ndly, to assert that 

 less is known on the subjects on which he has written than we are 

 willing to allow. 



Not taking into account collateral issues raised by the Colonel 



^ I feel bound to notice the strange way in which Col. Greenwood has so often 

 used my name alone in his letter, witliout any reason, as the paper he notices is the 

 joint work of Mr. Bristow and myself. — W. Whitaker. 



