76 THE DIFFERENCES BETWEEN 



the description of the latter which follows would lead 

 us to infer that the color was here different (it is said to 

 be "yellowish, marbled with blackish"). In young of 

 both turtles the latter description is applicable, for they 

 are then marbled beneath. For adults the description of M. 

 geographicus with reference to this point is right, for both 

 species are when nuiture of a dingy yellow color beneath, 

 the marbling having been gradually lost during growth. 

 The remainder of the description, "carapace strongly 

 notched behind and usually decidedly keeled," applies to 

 both species. 



COLOR. 



The ground colors and the pattern of coloration are very 

 similar in the two species compared stage for stage. They 

 agree almost line for line and spot for spot. Thus, while 

 a casual look at the dorsal sides of the heads of two young, 

 one of each species, seems to show that M. geographicus 

 has more yellow lines on this part of the head ; close look- 

 ing shows that with several conspicuous lines on the head 

 of M. lesueuri are others more obscure, and that in reality 

 the lines are nearly the same in number and position as in 

 the related species. 



The mark which will in most cases serve to distinguish 

 M. lesueuri from M. geographicus is a yellow, comma- 

 shaped spot behind each eye. Each spot begins near the 

 posterior border of the eye, in line with the nostril, ex- 

 tends inward, sometimes a little forward, then turns pos- 

 teriorly still nearing the middle line and growing narrower 

 and, finally, passing into a yellow line which extends pos- 

 teriorly on the neck. Sometimes one or both of the spots 

 are detached from the neck line. In some cases instead 

 of curving uniformly towards the middle line the spots 

 may be a trifle expanded and angulated opposite the dor- 



