the dental base; the outer side of the tooth is sculptured like the rest of the bone, but in a less or finer degree (see the magnified view, fig. 5, a). At rather less than a line in advance of this tooth is a minute one like the fourth ; in advance of this is the base of a larger denticle (ib. b), the fracture of which shows a cavity filled by pyritic matrix; and at a line in advance of this is the fractured hollow base of a smaller denticle: these hollows might at first sight be mistaken for sockets.
The alveolar border of the left side of the upper jaw (Pl. XVI. fig. 2, & fig. 6, magnified two diameters), continued further forward than that of the right side, shows, at a part wanting on the right side, a more advanced tooth (c), of the same shape as the fifth (a) from the hindermost on the right side, but somewhat larger ; its apex is more obtuse and seems to have been worn. This tooth is also a direct continuation of the bone, with the osseous sculpturing more feebly marked than on the jaw, the tooth appearing smooth to the naked eye. The bases of two smaller denticles appear in the 3 lines extent of alveolar border in advance of this tooth.
Thus we have evidence of about twelve of the maxillary teeth or tooth-like processes—two large, divided by an interval of about half an inch, the rest small or minute—all compressed, triangular, pointed, arming the hinder inch and a half of the alveolar border on each side of the upper jaw.
This dental character is more distinctly displayed in the corresponding parts of the alveolar border of the lower jaw. On the right side (P1. XVI. fig. 1), in an extent of 8 lines from the suture of the dentary (32) with the surangular (31), are five denticles (fig. 5, magn. 2 diameters): the hindermost is as minute as the one above; the next is somewhat larger; the third (d) is much larger, though not so large as the fifth (a) above, behind which the point of the third below projects. The fourth tooth below (counting forwards) is minute, the fifth (e) suddenly enlarged, especially in length, to 3 lines, with a breadth of base of 1 line; it is sharp-pointed, directed obliquely upward and forward. These teeth are processes of the bone; and the outward markings are strongest near the apex.
In the left dentary (Pl. XVI. fig. 2 & fig. 6, magn. 2 diams.), along an inch extent of the hind part of the alveolar border, are three of the larger laniariform teeth (ib. ib. d, e, f), divided by intervals of from 3 to 4 lines, in which are minute denticles.
The lower laniaries are longer and more slender than the upper ones; they are similarly directed, with their summits slightly inclined forward.
On an estimate of the extent of the dentigerous borders of the jaws at 3 inches, and a conjecture that the larger teeth were continued at the same intervals (as shown in the fossil) to the ends of the restored jaws, there would be ten of these teeth on each side of both upper and lower mandibles ; the intervening denticles would be about double that number (see conjectural restoration, fig. 8, Pl. XVI.).
The strictly avian character of the skull, on which this quasi-
