688 



PKOF. H. G. SEELET ON THE REPTILE 



The shaft (fig. 11) rapidly contracts, so that at a little below the 

 articulation it is hardly more than J centim. wide ; but it gradually 

 expands distally to 1 centim. The bone is compressed from above 

 downward ; its thickness in the upper half of the shaft is 4 millim.; 

 but it increases in the lower half of the shaft to over 5 millim., 

 owing to the development of a median ridge which divides this part 

 of the bone nearly equally into internal and external areas, which 

 are margined laterally by ridges. The inferior surface is also 

 marked towards the distal end by a slight longitudinal median ridge ; 

 and the articular end of the bone is subreniform, convex from side 

 to side. The width of the distal end (fig. 12) is 1 centim. ; and its 

 thickness in the middle is about J centim. The distal ridges are an 

 important distinctive character not found in living Crocodiles. 



Cervical Vertebrce. 



The cervical vertebrae are probably about the third and fourth. 

 What I take to be the third is only the centrum, and, except in less 

 development of the tubercle for the ribs, differs in no essential point 

 from the better-preserved bone. The fourth vertebra (PI. XXX. 

 figs. 6, 7) might, indeed, be the fifth, sixth, or seventh, since it pre- 

 sents all the characters seen in the vertebrae of the Alligator in the 

 middle of the neck. It is about the size of the vertebra figured by 

 myself as that of Crocodilus cantabrigiensis, but is shown to belong 

 to a distinct species by the less antero-posterior length of the neural 

 arch, its greater inclination forward, the stronger development of the 

 hypapophysial spine, and minor characters. 



The centrum is 17 millim. long, terminates posteriorly in a well- 

 rounded articular ball which is about 4 millim. long, and is margined 

 below by a sharp ridge and above by an equally sharp incised groove 

 (which may perhaps indicate a certain incompleteness of ossification). 

 The ball is circular and as nearly as may be a centimetre in diameter. 

 The cup in front is of corresponding size and form. The hypapo- 

 physis is a strong compressed process which rises just in front of the 

 ridge bounding the posterior articulation, and is directed forward 

 and downward in front of the anterior cup, much as in the fifth 

 cervical of the Mississippi Alligator. On each side of this process 

 and below the middle of the side of the centrum, but rather higher 

 than the corresponding process in the Alligator, is situate the parapo- 

 physis or articulation for the rib. It blends with the margin of the 

 anterior cup, and is a strong, compressed, triangular process with a flat- 

 tened facet which looks obliquely outward and forward. It is sepa- 

 rated from the hypapophysis by the usual concave channel (fig.6); and 

 a similar channel divides it from the diapophysial process on the neural 

 arch ; but in the middle of this channel, or, rather, towards its upper 

 part, is a slight ridge which extends from the upper margin of the 

 anterior cup backward towards the ball. The diapophysis, as usual, 

 extends further outward than the parapophysis, and is a smaller 

 facet supported on a process of which the hinder margin is no more 

 free than in the third vertebra of the Alligator ; but the process is 



