Prof. R. Owen on the Skull of a dentigerous Bird. 73 



granite ridges. But in some cases the basins were excavated in the 

 latter; Loch Leckan was mentioned as an example. It is about a mile 

 long, from 100 to 200 yards broad, and no less than 18 fathoms deep. 

 At the top of its southern bank, which consists of granite, there is 

 another lake (Loch-na-Craig), about 200 yards broad and 9 fathoms 

 deep. The surrounding hills are low, and there appeared to be no^ 

 source which could furnish ice to'excavate a lake of such depth as Loch 

 Leckan ; and further, the author contended that if one of these two 

 basins had been excavated by ice, the other could hardly have been 

 preserved intact. Two other lakes, excavated on the summits of 

 granite ridges, were mentioned ; and the author could not conceive 

 how either a glacier or an ice-cap could have produced such basins. 

 The Dhu Loch, separated from Loch Fyne by a bank of gravel about 

 a mile broad, is entirely in detrital matter, which the author thought 

 might have been accumulated in its present form by the sea beating 

 against the end of a glacier. Prom its position and level, the Dhu 

 Loch rises and falls with the tide; and it would appear that it 

 formerly extended some miles further up the valley, where the 

 author had found clays containing a mixture of marine and fresh- 

 water Diatomacese. In five of these cases the author thought it was 

 impossible that the basins are due to glacial action. 



2. " Description of the Skull of a dentigerous Bird (Odontopteryx 

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

 Richard 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 occupied by 

 several of the smaller denticles. Ail the denticles are of a triangular 

 or compressed conical form, the larger ones resembling iania- 

 ries. Sections of the denticles show under the microscope the un- 

 mistakable characters of avian bone. The length of the skull be- 

 hind the fronto-nasal suture is 2 inches 5 lines ; and from the pro- 

 portions 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 5 and 6 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 aquaticw. 

 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 superorbital gland-pit, limits the comparison to the Totipal- 

 mates 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 



