6 BRITISH FOSSIL REPTILES. 



some vertebrae a low and narrow ridge extends from the neur- to the pleur-apophysial 

 surfaces, as at c, fig. 4. 



The degree of concavity of the sides of the centrum in the anterior cervicals, 

 exposed in the specimen figured in Tab. Ill, fig. 1, has been exaggerated by the pressure 

 to which it has been subject, the effects of which are more conspicuous upon the skull : 

 the cancellous mid-part of the centrum has opposed less resistance than the compact 

 articular ends. 



The atlas (a) has been disarticulated from the occipital condyle (l) ; the hemispheric 

 articular cup is thus well displayed, with its smooth and shining surface. The coales- 

 cence of the centrums of the atlas [a] and axis (a) is complete. A tubercle from the 

 side of the centrum of the atlas represents the pleurapophysis ; its neural arch is 

 broken away ; that of the axis developes a spine similar to and but little smaller than 

 that of the third cervical. 



The dimensions of the seven vertebrae here preserved in connection with the skull 

 will be seen in Tab. Ill, fig. 1, where they are figured of the natural size. The 

 average dimensions of a cervical centrum of the present species, from the middle and 

 basal half of the neck, are, as in figs. 4, 5, 6 — 



In. lines. 



Length . . ; . 14 



Breadth of articular surface 16 



Height of middle of ditto ......... 13 



Length of costal pit ..... . ... 6 



Transverse diameter of outlet of neural canal ..... 6 



Dorsal series. — The transition from the cervical (Tab. I, c) to the dorsal series (ib., d) 

 is effected by the usual elevation of the costal surface by gradational steps, continued 

 through about five vertebree, until a single costal surface is presented by a large 

 diapophysis from the neural arch. The number of cervical vertebrae so defined in the 

 specimen figured in Tab. I is forty-one. In the first dorsal, characterised by the dia- 

 pophysial support of the rib (Tab. IV, figs. I and 2, d), the non-articular part of the 

 centrum is smoother than in the cervical vertebrae, the ridges or rugae occupying a 

 smaller extent near the two ends, where they indicate the attachments of the capsular 

 ligaments. The longitudinal concavity between the two ends is uniform and rather 

 more than in the cervicals. The venous foramina are wider apart and not divided by 

 any special transverse convexity on the under surface of the centrum. A vertical ridge 

 leads from the side of the centrum (ib., c) to the under part of the diapophysis (ib., «/), 

 nearer the hind than the fore end of the centrum. 



The diapophysis is convex and longest superiorly ; the fore part is rather hollowed, 

 the hind part flattened, and both converge to the ridge forming the shorter under 

 surface. The articular surface C^) of an irregular oval form, with the small end down- 



