Hector. — On the Fossil Reptilia of New Zealand. 339 



becoming thinner as they extended outwards, and also towards the fore and 

 hind parts of the bone, both of which ends were broken away. On one side the 

 surface of the bone is convex lengthwise, and slightly concave transversely. 

 On the opposite side the 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 the author regards the above described parts of the New 

 Zealand fossils as being homologous bones. But a more decided evidence of 

 the Plesiosaurian nature of this antipodeal fossil is afforded by the vertebral 

 centrums. They have flat articular ends, with two large and two small 

 venous foramina beneath. The neurapophysial surfaces, showing the persistent 

 independence of the neurat arch, are separated from the costal surfaces by 

 about half the diameter of the latter. These are of a full oval figure, 1 inch 

 3 lines in vertical, and 1 inch in fore-and-aft, diameter. On one side of one of 

 the centrums the rib has coalesced with the costal surface. The following are 

 the dimensions of this centrum : — Length 1 inch 9 lines, depth 2 inches 

 2 lines, breadth of articular end 3 inches 6 lines. The non-articular part of 

 the centrum offers a fine silky character."* 



To this same species I refer the specimens marked No. 1 b and d in the 

 collection of the Colonial Museum. 



No. 1 b. — This consists of the thoracic segment of the trunk of a young 

 individual. The dorsal surface of the animal has been worked out of the hard 

 matrix of the slab so as to expose ten posterior dorsal segments with ribs. 

 No vertebral centra are exposed in sitd, but scattered on the slab among the ribs 

 are four belonging to the dorsal region, and about twelve to the caudal, together 

 "with the smaller bones of the paddles. The thoracic ribs, a few abdominal 

 ribs, and the dislocated bones of the pelvic arch and appendages, complete the 

 specimen, which measures 2 feet square. The matrix is the usual grey cement 

 stone, containing an excess of lime, which is crystallized out in cracks, the 

 vertebrae, for instance, being split through the neural spines by a thick vein 

 of calcspar that traverses the entire length of the column, and is continued so 

 as to intersect the femur of the right side. The neural spines project 

 1"5 inches above the transverse processes. They have rounded tips, are 

 1"3 inches in antero-posterior width, with zygapophyses projecting •4: inch. 

 The transverae processes are 1 "7 inches long, cylindrical, and of the same size as 

 the ribs, to which they are attached without any expanded facet, either on the 

 process or the head of the rib. 



The ribs, which are directed backwards on the spine as they lie in the 

 * Owen, Proceedings of Brit. Assoc, 1861, p. 122. 



