PATTXA OF THE GrOSAU FOKMATION. 



689 



broad, and denned below and in front by an oblique groove. The 

 vertical measurement across the two facets for the cervical rib is 



1 centim. The neural arch has a decided aspect of being inclined 

 forward, owing to the way in which the slight rounded ridge from 

 the diapophysis ascends obliquely forward towards the praezygapo- 

 physis, coupled with the fact that the posterior border of the neural 

 canal is straight and parallel to it. The antero-posterior measure- 

 ment of the neural arch below the zygapophyses is less than a centi- 

 metre. The sides of the neural arch are concave from above down- 

 ward, and obliquely channelled. The praezygapophyses are strong pro- 

 cesses compressed into a wedge-shape in the usual way (fig. 7), directed 

 upward, forward, and outward, with circular facets, which are divided 

 from each other by a broad Y-shaped notch. The processes are 

 united by a thin platform above the neural canal, the anterior half 

 of which is excavated by a longitudinal pit which almost, or quite, 

 perforates the forked depression between the zygapophyses. Prom 

 the hinder half of the neural platform, which has a remarkably four- 

 cornered appearance owing to the lateral constrictions, rises the 

 neural spine. It is triangular, being compressed in front and wider 

 behind, where it is vertically channelled ; and the channel descends 

 so as to divide the posterior zygapophyses from each other. The 

 antero-posterior measurement of the base of the spine is f centim. 

 Its height, as preserved, from the base of the zygapophysial facet is 

 1^ centim. A slight ridge extends from its anterior border to the 

 posterior border of the praezygapophysial facet, while in the Alli- 

 gator the corresponding ridge, when it exists, is carried forward ; 

 behind this ridge the platform at the base of the neural arch rounds con- 

 vexly on the side of the centrum. The posterior z}-gapophyses (fig. 6) 

 are strong wedge-like processes directed outward, only slightly ex- 

 tending behind the neural spine, and not entirely behind it as in the 

 Alligator. They are remarkable for the well-defined notch below 

 them, something like that seen in the third and fourth vertebrae of 

 the Alligator, and for the tubercle above the posterior margin of the 

 ovate facets, which gives the back of the zygapophyses a somewhat 

 channelled appearance, to which, the Alligator offers no parallel. 

 The measurement from back to front over the zygapophyses is 



2 centim. The transverse measurement over the praezygapophyses 

 is about 18 millim. The side-to-side measurement of the constric- 

 tion between the anterior and posterior zygapophyses is 12 millim. 

 The posterior zygapophyses were evidently narrower than those in 

 front by a millimetre or two. The neural canal is transversely ovate 

 behind, but in front appears wider and more depressed (fig. 7), with 

 a flat wall ; the floor of the centrum is concave, and shows the usual 

 pair of nutritive foramina. 



Dorsal Vertebrce. 



There are 8 dorsal vertebrae, which mostly belong to the hinder 

 part of the series. Beckoning as the first dorsal that vertebra in 

 which the rib is for the first time entirely carried on the transverse 

 process, I should regard the earliest vertebra preserved of this 



Q.J.G.S. No. 148. 2z 



