THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 93. SEPTEMBER 1865. 



XVI. — On a new Lizard, with Ophidian affinities, from the Lower 

 Chalk (Saurospondylus dissimilis). By Harry Seeley, 

 F.G.S., of the Woodwardian Museum, Cambridge. 



Professor Owen described the Raphiosaurus subulidens from 

 the Lower Chalk of Cherry Hinton, and I should perhaps have 

 been inclined to refer the vertebra here described from that 

 locality to the same genus, had not a sight of Mr. Carter's type 

 specimen shaken my faith in its reptilian character. So far as 

 external features go, there is nothing to suggest that it is not 

 the jaw of a fish. Even were it reptilian, it is so dispropor- 

 tionately large in comparison with this vertebra, that the iden- 

 tity of the two would still be doubtful. But Professor Owen 

 appears to know the vertebrae of Raphiosaurus; for, in the 

 'Palaeontology' (p. 311, 2nd ed.), it is on such evidence that 

 the species is said to be based. 



The Lizards yet known from the Chalk have proccelian ver- 

 tebrae with that simple structure of the zygapophyses in which 

 the front articulations are turned up and exposed, and the back 

 pair turned down. This structure, characteristic of most ver- 

 tebrae, would appear to result from the fact that the limbs sup- 

 port that part of the skeleton which is in front of them — a func- 

 tion manifest in the straight or upward tendency of the neck, 

 where each vertebra rests on its zygapophyses, and the down- 

 ward dh-ection of the tail, where the vertebrae hang without 

 support under the zygapophyses. 



The development and origin of these processes and the form 

 of the bones depend on the functions of the muscles, though in 

 a less degree than in the limbs, where bones appear to have 

 owed their very existence to muscular and functional action. 



But in Saurospo7idylus the vertebra has ten articular facets, as in 

 Serpents and in the Iguana Lizards, in which the neurapophyses 



Ann. 8f Mag. N. Hist. Ser. 3. Vol. xvi. 1 1 



