1869. ]} DR. J. E. GRAY ON THE TORTOISES. 187 
A second half-grown specimen agrees with the very large old 
specimen above noticed in the absence of the zygoma. 
2. MELANOCHELYS. 
The thorax oblong, three-keeled. Vertebral plates broad, six- 
sided. Skull rather depressed ; zygomatic arch imperfect, tapering 
behind, and not reaching the tympanic bone ; lower jaw weak ; the 
alveolar surface narrow, linear. ‘Toes strong, webbed to the claws. 
MELANOCHELYS TRIJUGA. 
Emys trijuga, Gray, Cat. Shield Reptiles in B.M. t. 37. f. 2 
(“E. subtrijuga,” not good, zygomatic arch too broad and extending 
to the ear-bone). 
Skull (as seen through the skin in the stuffed specimen) ovate, 
elongate, triangular in front; sides of the face nearly erect ; orbit 
lateral, subsuperior, large; nose rather narrow; crown rather con- 
vex, elongate rhombic, narrowed and produced behind; from the 
Melanochelys trijuga. 
hinder point to the back edge of the orbit more than once and one- 
half the distance of the latter from the end of the nose; zygomatic 
arch rudimentary, very slender, linear, extending from the middle 
of the back edge of the orbit to the upper part of the front edge 
of the large tympanic cavity, which has a narrow, rounded edge ; 
sheath of the upper jaw with a simple straight edge, without any 
