No. 2319. A NEW GEINESE ISOPOD— BOONE. 601 



moderately curved, tapering to a fine point, which is reflected ahnost 

 straight back on the carpus, but does not reach the merus. 



Male. — The male is similar to the female in general appearance, 

 but is distinctly smaller, the largest full-grown specimen being only 

 14.2 long and 8 mm. wide; the body outline is more elongate ovate 

 and only slightly convex; the telson is not quite so long and is more 

 rounded posteriorly ; the uropoda are relatively larger and are slightly 

 conspicuous dorsally; and the pleopoda cover almost the entire 

 ventral cavity, but not quite extending to its terminal margin. 



As is the case with many of the parasitic Cymothoidea, the present 

 species is not pronouncedly different in general appearance from its 

 allies; in fact, a superficial diagnosis would quite probably designate 

 it a form of Ichtliyoxenus japonensis Richardson, but a critical com- 

 parison of the entire series of specimens of the present species with the 

 entire series of /. japonensis Richardson, including the type material, 

 and likewise with the series of /. jelUnghausH Herklots in the United 

 States National Museum, augmented by careful study of all the 

 literature on the group Ichthyoxenus^ especially that of /. montanus 

 Schioedte and Meinert, of which no specimens were available, con- 

 sideration of this species being necessarily based on the text and 

 Schiodte's and Meinert's excellent figures of the various phases of 

 the species, establish beyond question the fact that /. geei is as dis- 

 tinct specifically as the three previously described members of the 

 genus. 



The adult females of /. ffeei are uniformly less asymmetrical in 

 contour than those of /. japonensis; the insertion of the head of geei 

 is distinctive; the number of ocelli and the shape of the eye of 

 geei differs from that of japonerisis; the posterior margin of the 

 first thoracic segment of geei is relatively a straight line, while in 

 japonensis this is uniformly recurvate. The proportionately larger 

 and broader telson and the relatively smaller pleopoda and ur«>poda 

 of the female is distinctive of geei, as are the uniquely different 

 seventh pair of legs. Finally, the differently shaped and proportion- 

 ately much smaller maxillipeds of geei preclude its confusion with the 

 other members of the genus. 



It is interesting to note that all the so far recorded hosts of the 

 members of the genus Ichthyoxenus are confined to the fresh-water 

 fishes of the closely related families Cobitidae and Cyprinidae. 



Type.—Kn adult fem.ale. Cat. No. 53304, U. S. N. M., and an adult 

 male paratype, were found parasitic in " Tsi-fish," or carp, probably 

 Gyprinus carpio Linnaeus, taken from lakes and canals around Soo- 

 chow, China. The following additional paratypes — two males, one 

 female— and about 40 very young specimens, Cat. No. 53305, 

 U. S. N. M., were likewise collected by Prof. N. Gist Gee, of Soochow 

 University, for v/hom I take great pleasure in naming the species. 



