REPTILIA. 79 



From Brickhill also a few small vertebra3 have been obtained, 

 some of them belonging to the species just described, and others 

 (PI. I. figs. 3, 3a) with a very transverse short centrum, the sides 

 and articular faces nearly flat, and the outline of the latter roughly 

 trapezoidal. The neural arches are lost, their osseous union with 

 the centrum having been, as in Ichthyosaurus, incomplete. The 

 pair of pits on the ventral surface for the entrance of the nutritive 

 arteries is conspicuous in all the specimens. Measurements : 

 length 28 mm., breadth 48 mm., depth 39 mm. 



Some slender, curved, pointed teeth from Upware probably 

 belong to Plesiosaurus. Their surface is covered with small, very 

 continuous primary ridges, upon the sides of which there usually 

 exists a more delicate, crimpy crest. They measure 35 x 12mm. 



Pliosatjrtjs. 



Of the Pliosaurian teeth from Upware I cannot separate out 

 any that are likely to belong to the Lower Greensand age. A 

 number of vertebrae and fragments of paddles have occurred at 

 Upware, amongst which Mr Seeley has recorded {Cat. of Beptilia, 

 p. 76) VI. | " a peculiar new species," and v. d. ■£, a dorsal vertebra, 

 which is an instructive example, since it shews the epiphysis of 

 the centrum fallen away, just as occurs in the backbones of living 

 whales. 



Also fragments of the paddle-bones have occurred at Upware 

 which are remarkable for the shaft and epiphyses being often 

 separated. The latter having fallen out now look like gigantic 

 teeth or dermal spines, leaving the shaft as a double hollow cone 

 like a dice-box, or rather like an hour-glass, for the two cavities 

 are continuous. All these are probably ' derived ' fossils belonging 

 properly to the Upper Jurassic clays. 



Ichthyosaurus. 



Some conical teeth with square fangs found at Upware and 

 Brickhill are referable to the genus Ichthyosaurus. A fine speci- 

 men measures 60 mm. in length, of which the conical enamelled 

 biting portion occupies only 15mm. 



