218 DESCRIPTION OF REPTILES. 
Order CHELONIA. 
Genus CHELONE. 
Species. Chelone trigoniceps, Owen. 
More than one of the old tertiary Turtles (Chelone) are remarkable for the 
longitudinal extent or depth of the symphysis of the lower jaw. 
A species from the eocene clay at Harwich has this character so strongly 
developed, and the under surface of the symphysis so flattened, as to have sug- 
gested the ‘nomen triviale’ planimentum* for it. The Chelone longicepst, if we 
may judge by the length of the pointed upper jaw and bony palate, must have 
had a corresponding extent of the symphysis of the under jaw; and we may 
infer the same peculiarity from the straight alveolar borders of the maxillaries 
and their acute convergence towards the premaxillary bones in the allied species, 
Chelone trigoniceps (Tab. XIII. fig. 4), obtained from the eocene clay at Brackles- 
ham, and now in the valuable collection of G. A. Coombe, Esq. Amongst the 
Chelonites which Mr. Dixon has obtained from the same formation and locality 
are portions of the fore-part of the lower jaw of four individuals of the genus 
Chelone, all exhibiting the characters of the pointed form and great depth of the 
symphysis. 
One of these specimens (Tab. XIII. figs. 5 & 6) agrees so closely in size and 
shape with the fore-part of the upper jaw (7b. fig. 4)—fits, in fact, so exactly 
within the alveolar border, and so closely resembles that specimen in texture and 
colour, that, coming from the same formation and locality and being obtained 
by the same collectors, I strongly suspect it to belong to the same species of 
Chelone, if not to the same individual. 
The known recent Chelones differ among themselves in the shape and extent 
generally enveloped in sand: the plan I pursue is never to wash the specimens, but let them gradually 
dry, scraping the sand off by degrees with a small knife, and finally using a soft brush; when the sand 
has been entirely removed, a coating of diamond cement and water (equal parts) adds greatly to their 
preservation. I know of no greater pleasure that could be afforded to a paleontologist than the dis- 
covery of the head of one of these serpents. That enormous serpents lived and died in great num- 
bers in England during the Eocene period is a fearful truth of geological evidence, and persons un- 
acquainted with the more extraordinary creatures which are discovered in older formations, are ready 
to express their thanks, that these large snakes are no longer existing in our own country.—F. D. 
* Trans. of British Association, 1841, Report on British Fossil Reptiles, p.178. + Jbid. p. 177- 
