THE GEOGRAPHIC TURTLES. 75 



The sutures between dorsal plates are always exposed, 

 and the imbrication referred to is a slight projection of the 

 dorsal tubercle posteriorly seen in some young examples. 

 In adults this tubercle does not commonly extend beyond 

 the posterior outline, and the posterior extremity of the 

 tubercle is in some examples as far in front of the poste- 

 rior margin of its plate as it extends in others beyond it. 

 In addition to which the tubercles are quite evident in M. 

 geographicus and in young examples may show a tendenc}' 

 to project beyond the posterior edge of the plates. The 

 statement that the markings of M. lesueuri are less dis- 

 tinct was probably made after an examination of young ex- 

 amples. Of the two the adult M. lesueuri is generally 

 most brightly marked. Exceptions to this may occur, but 

 I think not many. Adult M. geographicus are certainly 

 very obscurely marked, though still maintaining much of 

 the original pattern. 



Similar objections may be urged against the account of 

 the geographic turtles in Dr. D. S. Jordan's Manual of 

 Vertebrates. 



The jaw is described as having a spoon -shaped dilation, 

 and the dorsal plates are said to be imbricated in M. le- 

 sueuri. The descriptions are good so far as they go, but 

 no important difference between the species is mentioned. 

 To illustrate, I will run briefly over the first one given, 

 that of M. geographicus. It is described as "dark olive 

 brown with greenish and yellow streaks and reticulations, 

 especially distinct on neck, legs and edges of carapace." 

 This will apply equally well to the other species with the 

 exception of the reference to the greenish lines. On large 

 examples the lines on the head and neck assume this color, 

 and I am not aware that they ever do so in M. lesueuri. 



The plastron is described as " yellowish." This will 

 serve just as well for M. lesueuri, notwithstanding that 



