52 Prof. Owen — New Zealand Plesiomurs. 



neck ; proportion of head to body ; shape and number of teeth ; 

 form, structure, and proportions of limb-skeletons, either in relation 

 to the trunk, or in that of the pectoral pair to the pelvic pair. In 

 short, materials have been wanting for assurance that the degree 

 of modification of the cervical vertebra, represented in PI. III., 

 may not have been associated with so much modification of the rest 

 of the skeleton as to warrant a generic section of Saiiropterygia, or 

 a subgeneric one in the Plesiosaurian family. I leave, however, to 

 him, who may have the good fortune to receive the requisite evi- 

 dence, the privilege of propoundiug the generic teiTu. 



Meanwhile, one has the satisfaction of seeing this type of Sauro- 

 pterygian cervical vertebra, which appears, with us, to be geologically 

 related to a Triassic deposit, repeated in fragments or boulders of a 

 broken-up part of, what the present evidence suffices to convince me 

 has been, an old Mesozoic shore or sea-bed in New Zealand. 



In Fig. 5 of Plate III. is given a reduced copy of a sketch of part 

 of the skeleton of a Plesiosauroid, in which twelve ribs of the left 

 side succeed each other. Whoever may glance at a specimen or 

 figure of a similarly preserved trunk of a Plesiosaurus, from the old 

 type Pies, dolichodeirus of Conybeare, now in the British Museum 

 (Trans, of the Geol. Soc, .2nd Sec, vol. i., pL xlviii.), to the Fles. 

 homalospondylus of my last Monograph on the subject (vol. for 1865 

 of the Palaeontographical Society, tab. v.), will appreciate the generic 

 character of the ribs in the New Zealand fossil. They are robust, 

 Bubcircular in section, expanding somewhat, or thickening, at their 

 middle, obliterating there, or leaving very little of intercostal space, 

 at least in the collapsed condition of the chest : they are, likewise, 

 solid (as indicated by the representation of a fractured end). 



The extent, in a straight line along the mid-part of this costal 

 series, is about 18 inches. The extent of vertebral column to which 

 they have been articulated may be reckoned, accordingly, to have 

 included twelve vertebrge, averaging an inch and a half in length. 



Now, this is the fore-and-aft diameter of each of the five consecu- 

 tive cervical centrums £gured at the fore part of the costal series. 

 If the foremost is rather shorter, the hindmost proportionally gains ; 

 but the increase of breadth is more marked than that of length, as is 

 usual at the base of the cervical series in Plesiosaurus. The diagram- 

 matic character of Dr. Hector's drawing — perfectly trustworthy in 

 reference to general form and dimensions of the bones — leaves me 

 in some doubt whether the riblets be indicated by the fractured 

 anchylosed bases, or by pleurapoiDhysial articular surfaces. In 

 either case, these elements projected from the low level of the 

 centrum, as in the single vertebra, Figs. 1-3. The foremost vertebra, 

 represented in the sketch, from which the proportion figured in Plate 

 III., Fig. 5, is reduced, is a cervical seen from an oblique side view, 

 showing that the pleurapophysis is anchylosed, and its expanded end 

 ■ — if it had an expanded end — has been broken of. But the diff'erence 

 in the fore-and-aft as compared with the transverse diameter in each 

 of the eight cervical A'crtebra) in the sketcli — there are two intervening 

 between the consecutive five and the detached one — forbids my refer- 



