60 MR. R. LYDEKKER ON THE [Feb. 19, 



1. On a Skull of the Chelonian Genus Lytoloina. 

 By R. Lydekker, B.A., F.Z.S., F.G.S., &c. 



[Eeceived January 28, 1889.] 

 (Plates VI. & VII.) 



In the year 1849 Sir Richard Owen, in his ' Monograph of the 

 Fossil Reptilia of the London Clay,' Part I. Chelonia, published by 

 the Palseontographical Society, described and figured (p. 27, pi. xi.) 

 the imperfect skujl of a large Marine Turtle from the Lower Eocene 

 London Clay of Harwicli, then in the possession of the late Prof. 

 Thomas Bell, under the name of Chelone crassicostata. That 

 species, it may be observed, was founded on the evidence of the shell, 

 and it will be unnecessary on this occasion to enter on the question 

 as to whether the specific association of the skull and shell is or is 

 not correct. 



In that plate the specimen is figured of two thirds the natural size ; 

 one view showing the frontal aspect of the cranium, a second the 

 right side, and the third the inferior aspect of the mandible, which 

 is retained in its natural position. When the specimen was figured 

 only the frontal aspect of the skull and the inferior and part of the 

 lateral surfaces of the mandible were exposed, the whole of the base 

 and occipital region of the cranium being concealed by the hard 

 rock of the septarian nodule in which the specimen had been 

 embedded. Moreover, on the frontal aspect of the cranium nearly 

 all the outer shell of bone is wanting, the contour being mainly 

 indicated by a cast of the inner surface of the cranial bones. 



In the year 1863 this specimen was purchased, together with the 

 remainder of Prof". Bell's collection from the London Clay, by the 

 British Museum. There it has remained in its original condition 

 until the beginning of the present year, when, with the permission of 

 Dr. \A'oodward, the Keeper of the Geological Department, I put it 

 into the skilled hands of Mr. R. Hall, assistant mason in that 

 Department, by whom the skull of Miolania recently described by 

 Sir Richard Owen in the ' Philosophical Transactions ' was so 

 skilfully developed. An equally successful result has rewarded 

 his patience and skill in the present instance, and by carefully 

 chiselling away the extremely hard matrix from the base of the 

 specimen, the whole of the palatal and occipital aspects of the 

 cranium, with the exception of that portion concealed by tlie 

 mandible, is revealed in as perfect a condition as in any recent skull. 

 Indeed, I am unacquainted with any other specimen of reptilian 

 remains from the London Clay in which the bones are so perfectly 

 preserved, and have such a sharp and fresh appearance. 



Since this skull indicates a genus of Turtles totally distinct from 

 all existing types, the only cranial evidence of which is presented to 

 us, so far as English examples are concerned, by the present specimen, 

 and another skull preserved in the Woodwardian Museum at Cam- 



