THE AMERICAN NATURALIST [Vol. LIV 



crab and the relative width of the abdomen. Some of the 

 smallest have the narrowest abdomen. There is some 

 correlation between the character of the abdominal ap- 

 pendages, particularly the first pair and the width of the 

 abdomen. As shown in Fig. 6 A, B, this appendage does 

 not appear as much like that of the female of the same 

 size, Fig. 6 C, as would be expected were it strictly 

 female, yet it can not be said to be male-like, and the nar- 

 rowness of the abdomen may be responsible for the dif- 

 ference. 



The claws are like those of the female in all cases. 



After the foregoing account was written I have received 

 from Miss Rathburn a number of fiddler crabs, exactly 

 like those recorded above, from the collection in the Na- 

 tional Museum in Washington. They fall into the same 



