540 Mr. Oaven on species of 



which we observe in the humped or bent back of the Frog. But the vertebrae of 

 existing caducibranchiate Batrachians have their posterior auricular surface convex, 

 and are articulated, as is well known, by ball- and socket-joints: the biconcave 

 vertebrae, therefore, of the extinct reptile under consideration would indicate its 

 affinity with the more fish-like forms of the Batrachian order. The neurapophyses 

 are anchylosed completely, without trace of suture, with the vertebral body, which 

 is also a Batrachian character among existing reptiles : * they rise in the present 

 fossil vertically and parallel with each other, are nearly coequal in length with the 

 centrum, and are joined above by a broad and fiat basis of the spinous process, 

 from each angle of which the oblique or articular processes are continued ; the sur- 

 faces of these processes are flat ; the plane of the anterior ones looks upwards, that 

 of the posterior ones downwards. A long and strong transverse process is sent 

 off from each side of the base of the neurapophysial arch. The spinous process 

 arises from the whole length of the middle line of the neurapophysial arch ; it is 

 not very high (about half a line) ; its chief peculiarity is the expansion of its elon- 

 gated summit into a horizontally flattened plate, the sides of which slightly over- 

 hang the base of the spine ; the upper surface of this plate is sculptured by irre- 

 gular pits, and this character strongly indicates a similar structure of the flat bones 

 of the cranium. The large atlas of the Toad presents a similar flattening of the 

 summit of its elongated spine. The sides of the body of the vertebrae are smooth, 

 concave in the longitudinal direction, owing to the lateral compression of the part 

 below the transverse processes ; the lower part of the body slopes inwards on each 

 side to a median, inferior, slightly marked ridge. 



In comparing these vertebrae with those of other reptiles, extinct and recent, 

 although the biconcave structure is most prevalent in the species from strata below 

 the chalk, yet the anchylosis of the vertebral arch, the obliquity of the centrum, 

 the terminal expansion of the spine, and the depth of the articular depressions, 

 indicate the Batrachian character of the present vertebrae. The aquatic Salaman- 

 ders, including the gigantic species from Japan, and the great extinct Salamander 

 of Scheuchzer, with all the Perennibranchiate Batrachia, have both extremities of 

 the vertebra concave ; but these concavities are generally conical, not hemisphe- 

 rical, as in the fossil : the neurapophyses in the fossil are higher, the spinal canal 

 is deeper and wider, and the spinous process stronger and more expanded supe- 

 riorly, than in the lower Batrachians. 



The portions of ribs in the present fossil are few and small, but sufficient to in- 

 dicate that the extinct reptile in question possessed them longer and more curved 

 than in any existing species. Here then is demonstrated an important Saurian 



* This structure prevails in the vertebrae of certain extinct Saurians. 



