72 THE DIFFERENCES BETWEEN 



descriptions may be arranged, for convenience in com- 

 parison, as follows : 



M. geocjraphicus. 

 Head very large, with yellow 

 stripes but no spots. 



2. 



Shell not elevated, smooth, 

 ecarinate, serrated behind, with 

 irregular meandering yellow 

 lines. 



3. 



Feet and tail striped with yel- 

 low. 



4. 



Length six inches. 



M. lesueuri. 



Head moderate, with yellow 

 stripes and large, confluent 

 blotches. 



2. 

 Shell elevated, carinate. 



8. 



4. 

 Size of preceding. 



The descriptions are misleading in several particulars. 

 M. geographicus 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 confluent 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 

 large size. The remainder of the statement concerning the 

 shell of M. geographicus applies equally well to the re- 

 lated species. The same thing may be said of the descrip- 

 tion of the colors of feet and tail. There are no essential 

 differences between the two in respect to the color of these 

 parts. 



Adults of M. geographicus will average eight inches in 

 length at least and are often as much as ten inches long. 



