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XV. — On certain peculiarities in the Cervical Vertehrce of the 

 Ichthyosaurus, hitherto unnoticed. 



By Sir PHILIP GREY EGERTON, Bart., V.P.G.S. 



[Read June 8, 1836.] 



feOME of the facts contained in the present Memoir, were announced to the 

 Geological Society in a short notice, read May the 13th, 1835*. Since that 

 period I have followed up the inquiry by the examination of a great variety 

 of Saurian relics ; and I am now enabled to enter more fully into the details of 

 those facts, the bare occurrence of which was all I could safely offer in the 

 former communication. By the aid of the illustrations given in Pl. XIV, the 

 anatomical details will, it is hoped, be rendered sufficiently intelligible, to 

 enable the reader to judge of the accuracy of the conclusions, which I have 

 founded upon a consideration of them. 



Atlas and Axis. 



In the spring of 1835, I procured from Miss Anning (whose zeal and in- 

 telligence are well appreciated in the Geological community) a specimen from 

 the lias of the neighbourhood of Lyme Regis, showing the atlas of a small 

 Ichthyosaurus, apparently anchylosed to the second vertebra of the column. 

 Having directed her attention to this circumstance, she informed me that 

 though she had frequently found similar bones, yet it had never happened to 

 her to see them disunited, even when a dislocation of every other bone of the 

 animal to which they belonged, had taken place. In less than a week I re- 

 ceived from her an atlas, seven inches and a half in diameter, corroborative in 

 a remarkable degree of her former observations. The axis was firmly united 

 to it, and she assured me that this was the only instance, in which any two bones 

 had been found in contact, after she had collected a large portion of the ske- 

 leton to which it belonged. I have subsequently had opportunities of examining 

 nearly thirty specimens of all sizes, and probably of several species, in various 



* See Proceedings, vol. ii., No. 41, p. 192. 

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