On a new Epicaridan Isopod 



[Athelges takanoshimensis sp. nov.) from Eupagurus 

 samuelis Stimp. 



By 



S. Ishii, Eigakushi. 

 With Plate VII. 



During last summer, while staying at Takanoshima, an islet near 

 the entrance to the gulf of Tokyo, my attention was called to an 

 Epicaridan Isopod belonging to the genus Athelges and found parasi- 

 tic on hermit-crabs which were kindly determined for me by Mr. 

 Terao to be Eupagurus samuelis Stimps. On study, the Athelges 

 turned out to represent a species which seems to be new to science. 

 I propose to call it A. takanoshimensis. 



As in other Epicarids, the species shows marked sexual dimor- 

 phism. The male is, as compared with the female, of a very 

 diminutive size besides being of a very different appearance, and is 

 usually found clinging to the metasome of the female in the manner 

 of a parasite. 



I. Adult female. 



The female is found attached, by means of its prehensile legs, to 

 the anterior part of the dorsal surface of the metasome of the host. 

 It stands in contact with the host surface by the entire extent of its 

 dorsal mesosome surface. Consequently, all the prehensile legs are 

 more or less twisted and dorsally directed. The marked concaveness 

 of the dorsal surface is due to the above mode of attachment. All 

 the females were invariably found with the head directed backwards 

 in relation to the host body. 



