no. 1995. THE ISOPOD GENU 8 ICHTHYOXENUS— RICHARDSON. 561 



ICHTHYOXENUS JAPONENSIS, new species. 



Body of female oblong-ovate, almost twice as long as wide, 13 

 mm. long, 7 mm. wide. Surface smooth. Color pale yellow, with 

 scattered black dots. 



Head small, triangular, 2 mm. long, 2 \ mm. wide; front rounded. 

 Eyes large, oblong, about 1 mm. in length and separated by a dis- 

 tance equal to 1 mm. or the length of one eye. First antennae short, 

 composed of six articles and extending to the 

 middle of the eye or to the end of the fifth ar- 

 ticle of the second antennae. Second antennae 

 composed of seven articles and extending 

 almost to the post-lateral angle of the head. 



The first segment of the thorax is about 

 twice as long in the median line as any of 

 the three following, being \\ mm. in length. 

 The second, third, and fourth segments are 

 subequal. The last three segments gradually 

 decrease in length, the three together meas- 

 uring \\ mm. v The anterior margin of the 

 first segment is sinuate in the middle, the 

 lateral parts projecting laterally beyond the 

 head and being posteriorly 

 constricted. Epimera are 

 present on the last six seg- 

 ments, those of the second, 

 third, and fourth segments 



being narrow, elongate plates occupying the ante- 

 rior half of the lateral margin; those of the last 

 three segments are about as long as wide, with the 

 posterior extremities rounded, and are placed just 

 anterior to the lateral margin of their respective 

 segments. 



The abdomen is deeply immersed in the thorax, 

 the lateral parts of the first two segments being 

 completely covered on one side, the second seg- 

 ment partly showing on the other side. The first 

 five segments gradually increase in length, all 

 together measuring 2\ mm. The sixth or ter- 

 minal segment is a little longer than wide, 

 mm. long, 4 mm. wide, and is posteriorly widely 

 rounded. Its posterior half is thin, semitranslucent, and colorless, 

 with no markings. The uropods are much shorter than the terminal 

 segment of the abdomen, and do not reach its extremity by a distance 

 equal to 1 mm. ; the branches are equal in length, narrow, tapering, 

 with rounded extremities, the outer one being slightly narrower than 

 the inner one. The pleopods are also short, not quite reaching the 



FlG. 4.— ICHTHYOXENUS JAPO- 

 NENSIS, Lake BrwA, from 

 acheilogn athus cyono- 

 stigma. Female, x 5. 



Fig. 5.— ICHTHYOXENUS 



japonensis, Lake 



BlWA, FROM ACHEI- 

 LOGNATHUS LIMB A- 



tum. Male. X 5f. 



