60 MR. R. LYDEKKER ON THE [Feb. 19, 
1. On a Skull of the Chelonian Genus Lytoloma. 
By R. Lypexker, B.A., F.Z.S., F.G.S., &e. 
[Received 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 Palzontographical Society, described and figured (p. 27, pl. xi.) 
the imperfect skull of a large Marine Turtle from the Lower Eocene 
London Clay of Harwich, 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. Woodward, 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 the 
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- 
