OF THE WEALDEN. 
255 
The bones of turtles, as well as those of the other 
oviparous quadrupeds of the Wealden, are generally 
of a dark brown colour, very heavy, brittle and 
strongly impregnated with iron. Their cellular 
structure is, in many instances, beautifully dis- 
played, being injected, as it were, with limestone 
or white calcareous spar ; and in numerous ex- 
amples the medidlary cavities of the long bones 
are filled with the same sid)stancc. There are, 
however, some remarkable exce})tions, in w'hich 
the bones are as light and porous as the osseous 
remains of diluvial deposits. 
IMonyx Bakeu'clli. 
Trionyx Bakewelli To the subgenus trionyx 
of M. Geoffroy, which contains freshwater turtles 
only, the specimen here figured bears the strongest 
affinity. The recent trionices are distinguished 
by the intervals between the ribs not being ossified 
throughout ; by their extremities not being ar- 
ticulated to an osseous border ; and by their sur- 
face being shagreened, and marked with little pits 
or hollow's, that the soft skin, the only integument 
