THE GEOGRAPHIC TURTLES. 79 
as distiiutly .so :it> in the other species. In the adult they 
are (|iiite black and are Iari>er. On each dorsal i)late is a 
})air of black dots, sometimes more. At the sutures l)e- 
tween adjacent costal plates are dark ])lotches, l)ut they are 
smaller and less distinct than in the other species. Blotch- 
es at the sutures between marginals are also present. 
The plastron of young M. geognqihicus is, as a whole, 
paler than that of M. lesueuri. The black of this region 
is not in this species so closely aggregated nor so exten- 
sive. In some examples it forms about a dozen isolated 
spots, each with concentric lines of pale yellow alternat- 
ing with the black. In other examples the black occupies 
most of the plastron, but the yellow areas within it give 
the eflect of a yellow^ plastron marbled with ])lack. In 
adults of both species the plastron is dingy yellow^ in col- 
or, sometimes with a trace of the dusky spots, but in large 
examples without any trace of the pattern which is so con- 
spicuous in the young. 
Apart from the features which have been mentioned, the 
two species resemble one another closely in color. The 
general color of the shell, body, head and limbs, the re- 
ticulation of the carapace, and the pattern in limbs and 
body furnish no ready means of distinguishing the spe- 
cies. 
FORM AND PROPORTION. 
In examples of young and adults which were measured, 
the depth of the shell was about the same tor the two spe- 
cies. An average of the dc[)th of four examples of each 
species, the two sets corresi)onding very closely as to size 
of individuals, showed 31. f/eofjixiphicus to be a trifle 
deeper. 
But a more uniform convexity of the carapace of 31. 
lesueuri conveys the impression of a deeper turtle. Ow- 
ing to this roundness of the carapace the length along the 
