376 Reports and Proceedings — 



The Duke of Argyll, in reply, agreed with Prof. Ramsay that it was not in all 

 cases that the lake-basins were due to disturbance of the rocks ; and indeed in 

 some of the most contorted districts lakes were rai-ely present. All his contention 

 was that whatever may have been the denuding agent, it was not in all cases ice. 



2. " Description of the Skull of a Dentigerous Bird (^Odontoptenjx 

 toUapicus, Owen), from the London Clay of Sheppey." By Prof. 

 Eichard Owen, F.R.S., F.G.S. 



The specimen described by the author consisted of the brain-case, 

 with the basal portion of both jaws. The author described in detail 

 the structure and relations of the various bones composing this 

 skull, which is rendered especially remarkable by the denticulation 

 of the alveolar margins of the jaws, to which its generic appellation 

 refers. The denticulations, which are intrinsic parts of the bone 

 bearing them, are of two sizes, — the smaller ones about half a line 

 in length, the larger ones from two to three lines. The latter are 

 separated by intervals of about half an inch, each of which is occu- 

 pied by several of the smaller denticles. All the denticles are of a 

 triangular or compressed conical form, the larger ones resembling 

 laniaries. Sections of the denticles show under the microscope the 

 unmistakable characters of avian bone. The length of the skull 

 behind the fronto-nasal suture is two inches five lines ; and from the 

 proportions of the fragment of the upper mandible preserved, the 

 author concluded that the total length of the perfect skull could not 

 be less than between five and six inches. The author proceeded to 

 compare the fossil, which he declared to present strictly avian 

 characters, with those groups of birds in which the beak is longer 

 than the true cranium, a character which occurs as a rule in the Aves 

 aquaticcB. He stated that none of the Waders have the nostrils so 

 remote from the orbits as in Odontopteryx ; and this character, with 

 the absence of the supraorbital gland-pit, limits the comparison to 

 the Totipalmates and Lamellirostrals. The former are excluded by 

 their not having the orbit bounded by a hind wall as in Odontopteryx, 

 and in this and other peculiarities the fossil seems to approach most 

 nearly to the Anatidse, in the near allies of which, the Groosanders 

 and Mergansers, the beak is furnished with strong pointed denticu- 

 lations. In these, however, the tooth-like processes belong to the 

 homy bill only, and the author stated that the production of the 

 alveolar margin into bony teeth is peculiar, so far as he knows, to 

 Odontopteryx. He concluded, from the consideration of all its 

 characters, " that Odontopteryx was a warm-blooded, feathered biped, 

 with wings ; and further, that it was web-footed and a fish-eater, 

 and that in the catching of its slippery prey it was assisted by this 

 pterosauroid armature of its jaws." In conclusion, the author indi- 

 cated the characters separating Odontopteryx from the Cretaceous 

 fossil skull lately described by Prof. 0. C. Marsh, and which he 

 affirms to have small, similar teeth implanted in distinct sockets. 



Discussion.- — Mr. Seeley had given much study to the Pterosaurians, to which 

 the author had indicated the affinities of Odontopteryx. He had in Ornithocheirt*s 

 Oweni found what appeared to be identical structure with that of the bird, and it 

 therefore appeared to form a new genus of Pterosaurians. Both in the frontal and 

 occipital regions of the skull he recognized affinities to Orniikoc/ieirus ; but it pre- 

 sented even more distinctly marked reptilian affinities. The position of the brain 



