THE GEOGRAPHIC TURTLES. 73 



M. lexneuri averages smaller, yet examples are frequently 

 seen that measure eight inches in length. 



The only statement concerning differences, therefore, 

 that can be accepted without important modification is that 

 with reference to the size of the head. The head of M. 

 geographicus is very large ; the head of M. lesueuri is rel- 

 atively small. 



De Kay's figure of M. lesueuri is good in the main, but 

 the markings about the head, if correctly drawn, were 

 from an unusually marked example. I refer to the two 

 large, comma-shaped yellow marks on the side of the head 

 posterior to the eye. In the majority of examples, at 

 least, there is but one of these marks, the more anterior, 

 and it is above the tympanum, never before or behind 

 it. 



Dr. Smith (Rep. Greol. Surv. Ohio, iv, 661) describes 

 the " head, neck and feet" as slender in both members of 

 the genus. The truth is that no member of the family 

 Emydidse occurring in the United States has a head larger, 

 relatively to the body, than the adult M. geographicus. 



The statement consequently applies to M. lesueuri alone. 

 On page 662 of the same paper the species are character- 

 ized thus ; 



Head and neck with yellow lines, often reticulated, and 

 a single spot on each side or none ; keel not very promi- 

 nent. G . geographica . 



Head with very large yellow blotches or stripes ; keel 

 very prominent. G. lesueuri. 



From this we are left to infer that there is a difference 

 between the turtles with respect to the markings of the 

 head. Yet as far as they relate to such markings the state- 

 ments might be transposed without loss in accuracy. The 

 head and neck of both are lined with yellow in much the 

 same pattern. In the great majority of both species also 



JSSSEX INST. BULLETIN, VOL. XXH 5* 



