"UPON HTPEEODAPEDON GOKDOKT. 



677 



skull and the hind limbs were relatively shorter in the extinct reptile, 

 but otherwise it must have had much the general aspect of its New- 

 Zealand ally — only, as I shall have occasion to point out more fully 

 by-and-by, the skull was relatively much broader and more massive 

 and the feet were shorter and stouter in Hyperodapedon. 



There are certainly 23 presacral vertebrae in Hyperodapedon, 

 perhaps 24, but I think not more ; Sphenodon has 25. In both 

 genera there are two sacral vertebras. 



In the first specimen, such of the thoraco-lumbar vertebrae as were 

 preserved were split through the middle vertically and longitu- 

 dinally. The sections of the centra showed that they were well- 

 ossified throughout, and they appeared to be terminated by slightly 

 concave contours. In the present specimen, the ventral faces of the 

 cervical, and of some of the anterior thoracic, vertebrae are exposed 

 and are almost uninjured; but from that which I reckon to be the 

 13th (though it may be the 14th) to the 20th, they are split horizon- 

 tally and longitudinally, the dorsal halves lying in the upper slab 

 and the ventral halves in the lower. The 21st., 22nd, and 23rd are 

 similarly split, but they are much injured. Now the ends of several 

 of these centra, notably the 13th, 14th, 18th, and 20th, present 

 a sectional contour, which in front is more or less convex ; while 

 behind it is similarly concave. The anterior ends of the centra 

 of the 4th (cervical) vertebra and of the 10th and 11th (thoracic) 

 vertebrae appear to be strongly convex from side to side and their 

 posterior faces correspondingly concave. Combining these appear- 

 ances with those seen in the longitudinal section, I can only suppose 

 that the surfaces must have been slightly cylindroidal, convex from 

 side to side in front, and concave in the same direction behind ; 

 and thus that they approximated, though very distantly, to those of 

 ordinary birds. 



The remains of the slightly displaced atlas (Plate XXVI. fig. 7) 

 are seen immediately behind the skull. It has the form of a ring 

 26 millim. wide and 20 millim. in vertical height. Traces of the os 

 odontoideum are visible immediately in front of the ventral portion 

 of the ring, which lies horizontally, with its ventral region turned 

 backwards. The front half of the second cervical vertebra is 

 broken away, but its centrum appears to have been about 20 millim. 

 long. The ventral faces of the third and fourth are well displayed. 

 Each is about 20 millim. long and 17 millim. wide at the ends, 

 but not more than 13 millim. at the middle. On each side of 

 the anterior end a short broad tubercle, which represents the 

 transverse process, is developed. I can find no indication of the 

 existence of intercentral ossifications. Each vertebra possesses a 

 pair of strong ribs (Plate XXYI. fig. 8). These lie at the sides 

 of the centra of the vertebrae and parallel with their length ; so that, 

 at first sight, the cervical region has a crocodilian look. The first 

 rib on the right side is well seen. It is a straight styliform bone, 

 40 millim. long and 3 millim. wide. On its dorsal side, and, more 

 or less hidden by it, lies the second rib, the remains of which have 

 about the same width and length. However, neither of these ribs 



