﻿KIMMERIDGE CLAY. 



47 



and teeth, and bones of the hind feet, are still desiderata. That not a single tooth 

 should have been met with in any part of the ossiferous matrix is much to be regretted, 

 but one indulges the hope that teeth of Omosaurus may be one day recovered and be 

 found implanted in their jaws. 



§ 2. Cervical Vertebra. — A portion of a neural arch and spine (PI. XI, figs. 

 1 and 2), with the right prezygapophysis, z , the left postzygapophysis, z \ the roof of 

 the neural canal, n , and the entire neural spine, n s, might belong, from the shortness 

 of the latter, to a caudal vertebra. But, from the indicated capacity of the neural 

 canal and the aspects of the articular surfaces of the zygapophyses, I infer the specimen 

 to have belonged to a vertebra from the cervical region. 



The length of the neural arch is 7 inches 6 lines ; the height of the neural spine is 

 3 inches 6 lines ; its fore-and-aft breadth, at the middle, is 2 inches ; at the free end 

 3 inches ; the thickness, transversely, is 1 inch : this is at the hind border, near the 

 summit ; it slightly decreases toward the base, and the whole spine thins toward the fore 

 part. The summit, which is rugged, gains in extent by being produced backward. 



The diameter of the neural canal appears to have been 1^ inches. The prezygapo- 

 physis, z, projects about half an inch in advance of the base of the diapophysis, d, d, 

 which here has an antero-posterior extent of 2 inches 6 lines. The outer border of the 

 prezygapophysis is slightly raised above the base of the diapophysis ; the articular 

 surface of the prezygapophysis looks upward and slightly inward ; it is not quite flat, 

 but feebly convex. The articular surface of the postzygapophysis, is in the same 

 degree concave. This surface looks downward and a little outward. 



In the figure of the upper surface of a cervical vertebra of a large Monitor Lizard 

 (Varanus niloticus, Cuv., PI. XI, fig. 4) I have indicated by dotted lines the course of the 

 fractures which have reduced the corresponding vertebra of the huge Dinosaur to the 

 condition shown in Fig. 2. The relation of the origin of the diapophysis, d, to the 

 prezygapophysis, g , is the same in both the recent and fossil Saurian ; but the breadth 

 across the zygapophyses was relatively less to the length of the neural arch in 

 Omosaurus. 



The fragmentary condition of this solitary evidence of the region of the vertebral 

 column supporting the skull seems to point to some strange violence by which the 

 head of the Omosaur has become severed from the trunk, and its frame-work probably 

 borne to some part of the old sea-bed at a distance from the rest of the body. 



§ 3. Dorsal Vertebrae. — Amongst the characters of the Order Dinosauria is a 

 lofty and buttressed neural arch in a great proportion of the trunk-vertebras. In 

 former Monographs this is illustrated in the Iguanodon (Suppl., No. II, Pal. vol. for 1857, 

 Tab. VII, figs. 4 — 6); in the Megalosaurus (Pal. vol. for 1854, ' Wealden Reptilia,' 

 Tab. XIX); in the Cetiosaurus (Suppl., No. II, Pal. vol. for 1S57, Tabs. VIII, IX). 



