4-44 



THE GEOLOGIST. 



ON THE REMAINS OF A PLESIOSAURIAN REPTILE (PLESIOSATJ- 

 RUS AUSTRALIS) FROM THE OOLITIC FORMATION IN THE 

 MIDDLE ISLAND OF NEW ZEALAND. 



By Pkofessor Owen, F.R.S., &c. 



The author, premising a quotation from his "Palaeontology," that "the further 

 we penetrate into time for the recovery of extinct animals, the further we must 

 go into space to find their existing analogues ;" and that " in passing from the 

 more recent to the older strata, we soon obtain indications of extensive changes 

 in the relative position of land and sea ;" cited some striking examples in proof 

 of these propositions from the reptilian class. The Mosasaurus of the creta- 

 ceous series occurs in that series in England, Germany, and the United States. 

 The Polyptychodon occurs in the same series at Maidstone and at Moscow. 

 Toothless Lacertian reptiles have left their remains in triassic deposits at Elgin, 

 in Shropshire, and at the Cape of Good Hope. Dicynodont reptiles occur in 

 the same formation at the Cape and in Bengal. The Plesiosaurus, with a more 

 extensive geological range through the jurassic or oolitic series, has left re- 

 presentatives of its genus in those mesozoic strata in England, and at her anti- 

 podes. Evidence of this extreme of geographical range had been submitted to 

 Professor Owen by Mr. J. H. Hood, of Sydney, New South Wales, obtained by 

 him from the Middle Island of New Zealand. This evidence 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 grey clay-stone, effervescing with acid ; the largest mass 

 contained impressions of pares 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 embedded in the Oxfordian or the liassic clays. The impression 

 of the first di apophysis and of its rib show the latter to have been 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 articular ends oppo- 

 site the interspaces of their diapophyses. The ninth rib had nearly resumed 

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

 it; the impression of the tenth rib shows the normal relative position of the pleuro 

 and diapophyses. The ribs are solid, of compact texture, cylindrical, slightly 

 curved ; the fragments looking more like coprolites 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. The first terminating in an obtuse end, of half 

 an inch diameter, is seven inches long ; the second is eight inches long; the 

 third is eight inches and a half; the fourth rib is nine inches long. The ex- 

 tremities ofthe others are broken off with the matrix. The separated fossils 

 sent trom New Zealand included the mesial co-adjusted ends of a pair of long 

 and broad bones thickest where they were united, and becoming thinner as 

 they extended outwards, and also towards the fore and hind parts of the bone, 

 both ot which ends were broken away. On one side, the surface of the bone 

 is convex lengthwise, and slightly concave transversely. On the opposite side, 

 tlie contour undulates lengthwise, the surface being concave, then rising to a 

 convexity, where a protuberance has been formed by part of the coadjusted 

 mesial margins of the bone ; transversely, this surface is slightly concave. A 

 similar but less developed, median prominence is seen at the middle of the 

 medially united margins of the coracoids in the Plesiosaurus Hawkinsii, and I 



