520 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25, 



glass slide. It showed large vacuities, especially at the attached base, 

 filled with pyritic matter ; and in the body of the tooth this matter 

 occupied and demonstrated part of the vascular canals. These show 

 chiefly a longitudinal course (PI. XVII. fig. 1, a), or in the direction 

 of the tooth's axis, united by short cross branches of minor diameter ( J ), 

 including oblong spaces ( e ). The general arrangement being thus 

 reticulate as in bone, the vascular substance not having filled a basal 

 conical cavity, like the dentinal pulp of a true tooth, a large propor- 

 tion of the osseous tissue of the process was preserved, showing, under 

 a magnifying power of 250 diameters (fig. 2), the bone-cells. These 

 have the proportions of length and breadth characteristic of the bones 

 of birds, and also of Pterodactyles. Many of the bone-cells were in 

 the direction of the long axis of the process, as at a, a (fig. 2), and 

 averaged in length -g-A- - of an inch ; others, nearer the vascular canals, 

 were arranged in a direction at right angles to the long axis of the 

 process, as at ft, 6, ib. : these indicated a short or transverse diameter 

 of the cell of Yih)~s °^ an i ncQ - The canaliculi from the bone-cells 

 were obliterated. Thus the microscopic test, in the degree in which 

 I have been enabled to apply it, shows the osseous characters of the 

 tooth-like processes, and adds to the probability of the conclusion 

 drawn from the external vascular markings, that they were sheathed 

 by hollow processes of the horny beak in the living bird. 



With the exception of the better-preserved canaliculi in the mi- 

 croscopic sections of the bone-tissue of a fossil femur of a bird from 

 Sheppey, figured by Quekett *, the size and shape of the bone-cells 

 are much alike in that and the present fossil from the same forma- 

 tion and locality. 



I conclude therefore that Odontopteryoc, like Archceopteryx, 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. 



The cretaceous fossil skull, affirmed by Professor 0. C. Marsh to 

 be that of a bird with teeth, and which he proposes as the type of a 

 genus under the name Ichthyornis, also of an order which he calls 

 " Ichthyomiihes," and of a new subclass of birds under the name 

 " Odontoenithes " or " Aves dentatce"f, differs from the Sheppey 

 fossil in having " the eyes placed well forwards," in having " the 

 lower jaw long and slender," in having " the teeth quite numerous 

 and implanted in distinct sockets," and in the size and shape of 

 such teeth. They are described as being " small, compressed, and 

 pointed, and all alike," or " similar." " Those in the lower jaw 

 number about twenty in each ramus, and are all more or less in- 

 clined backward." " The maxillary teeth appear to have been 

 equally numerous and essentially the same as those of the man- 

 dible "J. 



* ' Histological Catalogue,' Museum of the Koyal College of Surgeons, &c. 

 4to, vol. ii. plate x. figs. 34, 36. 



f American Journal of Science and Arts, vol. v. 8vo, February 1873. 

 J Id. ib. 



