Vol. 69.] SKELETON OF ORNJTHODESMVS LATIDENS. 381 



The Teeth. 



There are twenty-four teeth in the upper, and twenty-five in 

 ;the lower jaw. Only twenty-three of the former are exposed, 

 owing to a slight displacement of the upper jaw ; through this 

 derangement the teeth of the right dentary are covered by the 

 ^matrix underlying the teeth of the right premaxilla, in such a 

 manner that it is impossible to remove it, without endangering the 

 overlying teeth. The hindmost tooth on each side of the lower 

 Jaw is posterior to all the teeth of the upper. All the teeth inter- 

 lock. They are compressed laterally and lanceolate, the smallest 

 teeth being at the tip of the muzzle; these are followed gradually 

 by longer and broader teeth. The two posterior teeth on each side 

 of both jaws are broader, larger, and more bluntly pointed than 

 the rest. A very marked characteristic is that the last two teeth 

 of the mandibles fit into semicircular slots in the upper jaw 

 (PI. XXXVII, figs. 1 & 5) ; and the ultimate one of the upper 

 jaw lies exterior to the lower jaw, the lateral outer surface of 

 which is slightly concave to receive it but not slotted. These 

 teeth, in life, must have been visible when the muzzle was closed. 

 They are a little longer than the others. The indentations in the 

 upper jaw give an appearance to the last tooth of being set on the 

 summit of a strong process. The teeth are smooth and free from 

 strise ; but, on careful examination, there is to be discovered, on 

 the outer surfaces of some of them, an incipient median carina. 

 The alveolar borders of the upper jaw, anterior to the slots, are 

 -gently convex to the tip of the snout. Those of the lower jaw, 

 immediately in front of the last two teeth, fall abruptly some 

 distance below the plane of the tract occupied by those teeth, and 

 from there they are feebly concave. The posterior tooth of the left 

 ^dentary is displaced, but attached by matrix to the surface of the 

 bone near the dorsal border of the beak. This tooth is diamond- 

 shaped, both crown and base forming equilateral triangles. All 

 the teeth are vertical, and planted in separate sockets. 



The Vertebral Column. 



The hinder half of a cervical vertebra in. the Atherfield fossil is 

 ■quite similar to an example in the B.M. specimen R/176. That 

 example is much crushed, and has been fractured and -cemented 

 together, so twisted that the dorsal surface of the one portion is 

 followed by the ventral of the other. This is apparently the 

 example figured by Seeley 1 : it is proccelous. The neural arch and 

 spine are missing. In the Atherfield example the neural spine is 

 fairly high and robust, and the neural arches are flat and set at an 

 ■oblique angle to the spines : they overhang the centrum. The 

 neural canal is large. The centrum is long and narrow, becoming 

 moderately constricted in the central region. Laterally, a deep and 



1 ' Dragons of the Air ' 1901, fig. G6 & p. 17?. 



