Hector. -^0?i the Fossil Reptilia of New Zealand. 343 



3. Plesiosaurus hoodii, Owen. Geol. Mag., 1870, p. 51. 



Professor Owen named this species from the drawing of a single cervical 

 vertebra (3 d) obtained by Mi". Holmes at Waipai-a. These vertebrse, of 

 which several other specimens have since been obtained (both from the 

 Waipara, 3 h, and the Amixri Bluff, 3 c and 3 d), are easily distinguished by 

 their peculiar characters, which ai'e thus described, from the first discovered 

 specimen, by Professor Owen : — " It is broad and flat on the under surface of 

 the centrum ; the sides also of which, between the terminal articular surface, 

 are more flattened than usual, and converge towards the neural surface, giving 

 somewhat of a triangular figure to the vertical transverse section of that part. 

 The pleurapophyses come off from the lower part of the sides, and are 

 confluent therewith, like transverse processes. The characteristic pair of 

 venous foramina open upon the middle of the under surface. This vertebra 

 most resembles one from the bone bed of Aust-Cliff, near Bristol, described in 

 my ' Report on British Fossil Reptiles,' 1839, p. 78, and referred, with a note 

 of interi-ogation, to the Plesiosaurus trigonus of Cuvier. The articular surface 

 of the centrum is moderately concave, with a transversely oblong depression in 

 the centre, and the margin roxmded off. The neural arch is anchylosed to the 

 centrum. The neural canal is contracted, as usual in cold-blooded air- 

 breathers, and shows the ordinary proportion of that in Plesiosaurus. The 

 pleurapophyses are short and thick ; the fore and aft diameter of their base 

 equals two-fifths of that of the entire centrum ; they are somewhat inclined 

 downward, A distance of twice their vertical basal diameter intervenes 

 between them and the anchylosed base of the neurapophysis. 



"This vertebra gives the following dimensions : — 



Length of centrum ... ... ... 2 inches 1 line. 



Breadth of articular end of centrum ... 2 ,, 2 ,, 



Height of articular end of centrum, at middle 1 „ 7 „ 



"The JSTew Zealand specimen shows an exceptional form among the 

 extensive series of modified Plesiosaurian cervical vertebrae already defined or 

 recognized. Moreover, it is that form which hitherto, from British deposits, 

 has not been met with associated with other parts of the frame, yielding the 

 charactei'S of proportionate length of 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 j^elvic 

 pair. In short, materials have been wanting for assurance that the degree of 

 modification of the cervical vertebra may not have been associated with so 

 much modification of the rest of the skeleton, as to warrant a generic section 

 of SauTopterygia, or a subgeneric one in the Plesiosaurian family." 



The proportions of the specimen given above agree well with the cervical 

 vertebrse since obtained, although the actual dimensions vary somewhat. Thus, 



