Tortoise, and Lizard from the Chalk of Kent. 413 



With this evidence of the primary group of reptiles to which the fossil belongs, 

 there next remained to be determined to which division of Saurians having ball 

 and socket vertebral joints it was to be referred. In the Crocodilian, or Loricate 

 group, the transverse costigerous processes are elongated, the posterior ribs are 

 exclusively attached to these processes, and three, four or five of the vertebrEe 

 which precede the sacrum are ribless, and consequently reckoned as lumbar ver- 

 tebrae ; in the Lacertine Saurians there are never more than two lumbar vertebrje, 

 and all the ribs are supported on short convex processes or tubercles. 



In the present fossil each rib is articulated by a single head to a short process 

 of this kind, and they are attached to all the vertebrae except the one immediately 

 preceding the sacrum : these characters, with the slenderness and uniform length 

 of the ribs, and the degree of convexity in the articular ball of the vertebrae, prove 

 incontestably that the fossil is part of a Saurian appertaining to the inferior or La- 

 certine group. 



The costal tubercles are developed, as in other Lacertians, from the sides of the 

 anterior part of the body of the vertebrae ; the under surface of the vertebra is 

 smooth, concave in the axis of the body, and convex transversely. 



As there are twenty-one costal vertebrae anterior to the sacrum, including the 

 single lumbar, the fossil cannot be referred to the genera Stellio, Agama, Leiolepis, 

 Lyriocephalus, Basiliscus, Anolis, or Chameleon ; but a comparison may be insti- 

 tuted between it and the Monitors, Iguanas, and Scinks. In the absence of cra- 

 nium, teeth and extremities, any closer approximation of the fossil to existing forms 

 v;ould be hazardous, and too conjectural to yield any good scientific result ; and 

 the subjoined figure supplies the place of further verbal description of the propor- 

 tions of the different vertebrae. 



If the portions of the lower jaw of a Lacertian from the lower chalk, near Cam- 

 bridge, should be of the same species, as it agrees in size with that above described 

 from the same formation in Kent, there would then be no doubt that the chalk 

 Lacertian is generically distinct from any known existing Lizard. Fig. 3. PI. XXXIX. 

 is a side-view of a portion of the lower jaw of the Lacertian reptile from the lower 

 chalk near Cambridge. It contains twenty-two close-set awl-shaped teeth, anchy- 

 losed by their bases to an outer alveolar parapet of bone, as shown at fig. 'Sb. I 

 have proposed the name of Raphiosaurus for the genus indicated by this fossil. 



VOL. VI. SECOND SERIES. 3 H 



