72 
THE DIFFERENCES BETWEEN 
descriptions may l)e arranged, for convenience in com- 
parison, as follows : 
M. f/eof/raphicns. 
Head very large, with yellow 
stripes but no spots. 
M. lesueuri. 
Head moderate, with yellow 
stripes and large, contlueiit 
blotches. 
2. 
Shell elevated, cariiiate. 
Shell not elevated, smooth, 
ecarinate, serrated behind, with 
irregular meandering yellow 
lines. 
3. 
Feet and tail striped with yel- 
low. 
4. 
Leiigtii six inches. Size of preceding. 
The descriptions are misleading in several particulars. 
M. geograpJiicus always shows spots on the head. They 
are small relatively in large examples, but are always 
present and are quite characteristic. In young and half- 
grown examples they are almost as conspicuous as in M. 
lesueuri. M. lesueuri does not show continent blotches on 
the head. Spots are always present, but they are very 
constant as to position and form, are always well-defined 
and never, as far as I have observed, merge among them- 
selves or with adjacent yellow lines. 
The shell of M. geographicus is carinated, conspicu- 
ously so in youth, quite evidently so in individuals of me- 
dium size, and a carina is not wanting from examples of 
larsre size. The remainder of the statement concerning the 
shell of M. geograplii(MS applies equally well to the re- 
lated si)ecies. The same thing may l)e said of the descrip- 
tion of the colors of feet and tail. There are no essential 
ditierences l)etween the two in respect to the color of these 
parts. 
Adults of M. geograpJiicus will average eight inches in 
length at least and are often as much as ten inches long. 
