AN AUSTRAXIAN SAUKOPTERYGIAN — ETHEEIDGE. 25 



The centra in these vertebra are decidedly short, more propor- 

 tionately so than in Cimoliosaurus catHahridgiensis, Lydk.,* and 

 in this respect approach nearer to those of C. valdensis, Lydk.,t 

 and C. eurymerus, Phill.| There is not the slightest appearance 

 of any rugosity round the edges of the terminal faces of the centra 

 as in Plesiosaurus rugosus, Oweri,§ from the Lias, but they are 

 prominent and outwardly bevelled as in C. cantahridgiensis ; nor 

 is there any sinuous profile with overhaug of the upper border, 

 and prominence of the lower border of the centra as in the genus 

 Polyptychodon. The sides of the centra can hardly be described 

 as concave, although the ventral surfaces are fairly so on either side 

 the hseraal carina. The anterior and posterior articular surfaces 

 vary in contour from circular to subquadrate, the transverse dia- 

 meter being always the greater, with a well marked although not 

 thick border, surrounding a wide and fairly deep concavity or 

 cup. There are no mamraillse, or any trace of a pit in the vertebrae 

 examined. The venous or ha;mal foramina are situated in definite 

 depressions, well marked and deep, and in the best preserved 

 vertebra ISTo. 1, (PI. v., Fig. 4) three-sixteenths of an inch apart, 

 this being the transverse measurement of the hseraal carina. The 

 latter expands fore and aft in buttress formation into the anterior 

 and posterior peripheries of the terminal faces, producing on the 

 whole an hour-glass shaped figure, as in C. constricius, Owen. 

 The single costal facets are rarely seen in consequence of the 

 thorough union that has taken place between the head of the ribs 

 and the costal surface itself. In one, however (No. 2), where the 

 head of the rib appears to have broken out, the pit or scar seems 

 to be circular. The fore and aft borders of the neurapophyses 

 are vertically concave, the fore much more so than the hind, and 

 transversely are more angular than convex, particularly posteriorly. 

 The neuro-central suture is almost totally obliterated. Zygopo- 

 physial ridges, the prominent lateral oblique ridges extending from 

 the pre-zygopophyses to the posterior borders of the pedicle, can 

 hardly be said to exist. The pre-zygopophyses are rather high, 

 and in the only vertebra in which they are sufficiently preserved 

 No. 1, (PL v., Fig. 5), do not project forward beyond the vertical 

 line of the terminal face of the centrum, not even as much as in 

 C valdensis, Lydk., and C. limnophilus, Koken.|| The zygopo- 

 physial articular surfaces approach the oval in form, and are very 

 obliquely inclined, much more so than in either the last-named 

 species, C. cantahridgiensis, or C. eurymerus. The post-zygo- 

 pophyses are not preserved in the most perfect vertebra of the 



* Cat. Foss. Eeptilia and Amphibia Brit. Mus.,pt. ii., 1889, p. 183, f. 60. 



t Ibid, p. 188, f. 61. 



X Lydekker, Md, p. 206, f. 67. 



§ Mon. Foss. Eeptilia Liassic Formations, pt. i., 1865, p. 35. 



II Leydkker, loc. cit., p. 225, f. 69. 



