338 Transactions. — Geology. 



PYTHONOMORPHA, 

 Vertehrce concave in front, and convex behind. Teeth firmly attached to 

 the jaw ; never occur free in the matrix, except when broken off. 



A — LlODON. 



Dorsal vertehrce subprismatic, cup and ball of equal diameter. Teeth conical, 

 curved, with thick enamel, pulp cavity constricted at base. 



B — Taniwhasaubus, 



Dorsal vertebrae with the cup end expanded, and tapering obliquely to the 

 ball end. Humerus very short, wide, and with powerful muscular crests. 

 Teeth conical, with pulp cavity expanded at base. 



1. Plesiosaurus australis, Owen. Proc. Brit. Assoc, 1861, p, 122. 



As Professor Owen's description of the specimens on which he founded this 

 species is not accessible to many in the colony, I qiaote it at length. 



The specimens " consisted of two vertebral bodies or centrums, ribs, and 

 portions of the two coracoids of the same individual, all in the usual petrified 

 condition of oolitic fossils. Their matrix was a bluish-gz^ey clay--stone, effer- 

 TBScing with acid ; the largest mass contained impressions of parts of the arch, 

 and of the transverse processes of nine dorsal vertebrae, and of ten ribs of the 

 right side, Portions of five of the right diapophyses and of six of the ribs 

 remained in this matrix, The bones had a ferruginous tint, contrasting with 

 the matrix, as is commonly the case with specimens imbedded in the Oxfordian 

 or liassic clays. The impressio^ of the first diapophysis and of its rib, 

 show the latter to have beeq. articulated by a simple head to its extremity, 

 as in the Plesiosaurus ; but the succeeding rib had been pushed a little 

 behind the end of its diapophysis, and the same kind of dislocation had 

 placed the five following ribs with their ai'ticular ends opposite the inter- 

 spaces of their diapophyses. The ninth rib had nearly resumed its 

 proper position opposite the end of the diapophysis, but at some distance 

 from it j the impression of the tenth rib shows the normal relative 

 position of the pleur- and diapophyses. The ribs are solid, of compact 

 texture, cylindrical, slightly curved, the fragments looking more like ooprolites 

 than bone ; they are about an inch in diameter, with but small intervals 

 of, say, one^third of an inch, slightly expanding as they recede from the 

 transverse process, and slightly contracting to the lower end. TI>e first, 

 terminating in an obtuse end of -| an inch diameter, is 7 inches long ; the 

 second is 8 inches long ; the third is 8| inches ; the fourth rib is 9 inches 

 long. The extremities of the others are broken ofi" with the matrix. The 

 separated fossils sent from New Zealand included the mesial coadjusted ends 

 of a pair qf long and broad bones, thickest where they were united, and 



