PROF. H. &. SEELEY ON PSEPHOPHOEUS POLYGONUS. 411 



of the vertebral column to which they belong, though I am disposed 

 to believe that they chiefly pertain to the later cervical or dorsal 

 series, and there is a fragment which appears to be a portion of a 

 rib. The best-preserved specimen rests on its side, partly imbedded, 

 and fractured through its length. The centrum is about five and a half 

 centimetres long, or but little longer than the later cervical vertebrae 

 of Sphargis. It shows cancellous tissue along its fractured length ; 

 but in the processes this is covered by a dense outer layer. The base 

 is concave in length, the constriction being greatest towards the an- 

 terior end. The anterior end is cupped concavely, is about two and 

 a half centimetres deep, and has the articular cup vertical. The pos- 

 terior articular end was a well-rounded ball, and considerably deeper 

 than the anterior cup. The neural arch is, unfortunately, much less 

 perfect than the centrum. Projecting anteriorly just above the 

 neural canal is a small process ; and above this is the right side of the 

 neural arch, which reaches forward and upward in a wedge-shape, 

 having a total length, from its posterior termination near the middle 

 of the centrum, of about five centimetres, and gives no indication of 

 facets of the zygapophyses, which could not have looked inward. 

 Its total height from the base of the centrum, as preserved, is about 

 six centimetres ; the distance for which it extends anterior to the 

 articular face is about two and a quarter centimetres. Erom the 

 middle of the right side of the centrum, at about its junction with 

 the neural arch, is given off a transverse process, which has a strong 

 expanded base, is somewhat compressed, and directed outward and, 

 possibly, upward. It is imperfectly preserved at the end. Imper- 

 fect as these indications are, they amply show that we have here to 

 do with an animal which differs not only generically from Chelonians, 

 but in characters in which all other genera agree. 



Two other centrums are exposed so as to show their length. Both 

 appear to be moderately concave at the expanded anterior end, and 

 slightly convex at the narrower posterior end. These vertebrae are 

 about five and a half centimetres long. One shows the hinder part 

 of the centrum to be rounded from side to side (it probably had a 

 descending process in front) ; the other shows a strong flattened 

 transverse process, which is directed slightly forward, and expands 

 a little anteriorly towards its free end. The fourth fragment indicates a 

 smaller vertebra, apparently caudal, which has the prezygapophyses 

 strong and short, and curved apparently forward and upward, with 

 the facets looking inward. The points in which these vertebrae differ 

 from those of all Chelonian reptiles are, the apparently massive cha- 

 racter and great development and height of the neural arch, and the 

 extraordinary transverse processes, which are both ankylosed to the 

 centrum. 



In Chelonians such processes are limited to the caudal region ; 

 but in no respect have we here the characteristics of caudal vertebrae, 

 except in the small and imperfect specimen, in which the end of the 

 centrum appears to be flattened. And I believe the evidence rather 

 points to the vertebrae belonging to the later cervical or dorsal 

 region. 



