THE FOEEST-BED OE EAST ANGLIA. 



101 



rudimentary neural spine is at the middle of the upper surface in the former, and in 

 front of the middle in the latter. The dorsal nerve-foramina of C. giganteus are 

 constricted into a figure-of-8 shape (and completely divided by a bridge in a specimen 

 from the Barrington gravel in the Woodwardian collection), while they are long slits 

 in C. helgrandi. The neural arch of C. lelgrandi has a wider sinus behind on its dorsal 

 side ; its anterior dorsal emargination is more square-cut : the ventral depression behind 

 the nerve-foramen is much deeper ; the hypapophysis is most prominent behind, with a 

 median ridge passing towards the anterior end of the vertebra (that of the Woodwardian 

 specimen of C. giganteus having no ridge). In some of these latter points the Barrington 

 specimen holds an intermediate position between the two others. 



In the Axis : — The dorsal edge of the neural spinels thinner in C. helgrandi; the 

 transverse processes, which are incomplete, were probably less projecting; the posterior 

 zygapophyses are narrower (1*05 inches, as compared with 1"5-1'8 inches) and more 

 raised ; there is a distinct emargination between the posterior zygapophysis and the 

 neural spine ; and the ventral median ridge is distinctly higher and bounded by 

 deeper grooves at its sides than in C. giganteus. 



In the tables which follow, the measurements have been taken in such a way as to 

 permit of easy comparison with those given by Boyd Dawkins ', Belgrand^, and others. 



I. Skull. 



inches. 



Greatest length of the part of the skull preserved . 9-0 



Greatest breadth of the skull 8-1 



Occipital crest to fronto-parietal suture 4-1 



j^ „ pedicle (shortest distance) 3'0 



Interval between, pedicles 3-0 



,j „ supra-orbital foramina 3-9 



Erom burr to burr (shortest distance) 5-4 



J, „ (distance between outer edges) 10-4 



Top of foramen magnum to top of occipital crest 3-0 



Foramen magnum, height of 1"1 



width of ■ 1-4 



Frontal width, just below pedicles ■ '■ 7-3 



Pedicle, length of 1"^ 



„ circumference of .'..'.' • "'o 



„ antero-posterior diameter of -'4 



„ dorso-ventral diameter of ^'9 



Interval between bases of K. & L. brow-tines 9'» 



Brain-case, diameter (external) behind pedicles 4-6 



Distance between outer edges of condyles "^"^ 



millim. 



228 



206 



104 



76 



76 



99 



137 



265 



76 



28 



35 



185 



46 



215 



61 



74 



250 



117 



1 Pal. Soc, t. cil. pp. 25-28. 



^ " La Seine.— I. Le Bassin Parisien. Planches de Paleont.," 1869, p. 13. 



