Vlll INTRODUCTION. 



the true one, the position of the Athecata (if retained as a suborder) 

 should he at the opposite end of the series to that which it now 

 occupies. The absence of any limb-bones of Chelonia in the 

 Lettenkohle, where Psejphoclerma is common, is in favour of the 

 contention that the specimens so described are not Chelonian. 



Thanks are again due to Mr. William Davies, for kindly checking 

 the entries of the individual specimens, and for information in 

 regard to their history. 



The Bell Collection, mentioned for the first time in this Part, 

 comprises specimens from the London Clay collected by the late 

 Professor Thomas Bell, and purchased in 1863. 



The Brown Collection, made by the late Mr. John Brown, of 

 Stanway, Essex, was in part presented by the owner, and in part 

 by Sir R. Owen, K.C.B., in 1860. 



The Sloane Collection, also first alluded to in the present Part, 

 was purchased about the year 1 751 from the executors of Sir Hans 

 Sloane, of Chelsea. 



The Willcox Collection was purchased in 1853 from Mr. C. Willcox 

 of Swanage. 



KICHARD LYDEKKER. 



Harpenden, 

 November, 1889. 



