18 Pi'of. S. O. Seeleij — On the Genus Ornithochcinis. 



some respects to this species, I suspect it will prove to be dentary. 

 It, however, diflfers in presenting a nearer approximation to the type 

 of Oniithocheirus simiis, and it entirely wants the somewhat flattened 

 oblique inferior area, which in Oniithocheirus Eeedii is concave from 

 front to back. The teeth, however, are nearly circular. The species 

 now desci'ibed differs from Oniithocheirus capito (Ornithosauria, 

 p. 126), in the circumstance that the teeth in that species are elliptical. 



Obnithocheirus xyphorhynchus (Plate I. Fig. 2a and 26). 



This species was founded upon a fragment from the middle of a 

 lower jaw, which measures 5^ centimetres in length, and must have 

 presented an unusually dagger-like form. There is a narrow median 

 groove running along the palate. The base of this groove is sharp, 

 and its narrow sides diverge upward and outward, and round into the 

 palate, so that it appears to be margined by a ridge on each side, 

 about a millimetre wide. The palate is formed of two lateral 

 portions, which look obliquely upward and outward, and are inclined 

 to each other at a right angle. The width of the palate at its 

 outer limit is 13 millimetres ; the depth of the inclined 

 lateral halves of the palate is on each side about eight millimetres. 

 The palatal surface shows on each side four tooth-sockets, better 

 preserved on the left side than the right. The sockets are placed 

 on the outer part of the palate, at a distance of four millimetres from 

 the median groove. The interspace between the first two sockets is 

 eight millimetres, and between those which follow a trifle more. The 

 sockets are ovate, and placed obliquely so that the anterior margin of 

 the tooth inclines towards the inner part of the palate, and its hinder 

 margin towards the outer limit of the palate, where the bone is 

 elevated a little as usual.' The interspaces are slightly concave from 

 front to back, and the inner and hinder border of the tooth-socket is 

 more elevated than its anterior border. Prom this description it will 

 be seen that the inner part of the palate rises as a double ridge 

 between the teeth, and in length this ridge is very slightly concave. 

 The sides of the jaw below the teeth round continuously into the 

 inter-alveolar spaces, but they converge inferiorly into a blunt keel. 

 The side below the alveolus is twelve millimetres deep in front, and 

 increases a little in depth behind. It is gently convex and appears 

 to be impressed in the lower part by the longitudinal groove which 

 is parallel to the base. It is about half a centimetre from the base 

 on the right side, and a little higher and less distinctly marked on 

 the left side, especially in front. But for the convexity of the surfaces 

 above and below, I should have regarded it as the result of fracture. 

 Opposite the third pair of tooth-sockets are two holes with impressed 

 borders apparently due to teeth of a flattened character, such as 

 those of a Pycnodont fish. The larger of these impressions is seven 

 millimetres long. The outer layer of bone is a good deal scaled off 



1 The tooth-sockets are not uniformly of the same size. The earliest of the four 

 is the smallest, and the fourth is smaller than the third. The second socket is 

 7 millimetres in length and 4 millimetres in width. The teeth appear to haye heen 

 directed as usual upward, inward and a little forward. 



