73 



Sixth abdominal segment somewhat less than twice as long as the fifth. The male 

 pleopods have been described above; it may be added that the spine at the outer distal angle 

 of the antepenultimate joint of the exopod is even slightly longer than the sum of the three 

 distal joints and about as long as the strong, curved seta at the angle of the following joint 

 (fig. 2 k). The figure of the uropods of the male (fig. 2 ;/) as compared with that of the female 

 (fig. 2 ni) seems to indicate essential sexual differences in the shape and armature of the endopod, 

 but the differences observed are in the main due to the fact that the endopod of the male is 

 seen vertically from above, so that the lateral serrations, the places of insertion of the setae, 

 are visible along both margins, while an acute protuberance projects upwards and backwards 

 on the upper side a little from the outer margin, and the slender processes project inwards 

 and downwards from the lower side near the inner margin ; in the female (fig. 2 ;«) the endopod 

 has been turned a little round its longitudinal axis, with the result that the insertions of the 

 setae along the inner margin are seen on the upper surface, that those along the outer margin 

 are situated below and therefore invisible from above, that the acute protuberance mentioned 

 projects from the new exterior margin which shows a sharp incision or sudden break, and 

 finally that the inner processes project not from the lower surface but from the inner margin 

 and are directed horizontally inwards. In both sexes the distal half has 4 very strong, somewhat 

 curved processes, the proximal one being the longest and a little behind that a single, small 

 process is seen, while the larger distal part of the proximal half has almost a score of smaller 

 or small, acute processes. Telson somewhat more than half as long as the uropods (figs. 2 in 

 and 2 «), a little more than half as broad as long, tapering nearly from the base ; the posterior 

 incision about one-fourth of the total length of telson, with its margins convex without spines 

 or setae and the angular base subacute ; the lateral lobes are distally narrow, each terminating 

 in a moderately large spine, a little in front of which a somewhat smaller spine is found, and 

 each of the lateral margins besides with 8 — 11 spines, the first not far from the base. 



Length of an adult male 4 mm., of a female with marsupium 3.5 mm. 



Tribe 3. Mysini. 



To this very natural tribe a large number of genera are to be referred, viz. Stilomysis 

 Norm., Macropsis G. O. S. {= Parapodopsis Czern. and Mesopodopsis Czern.), Heniimysis G. O. S., 

 and the numerous genera into which the genus Mysis Latr. in the sense of G. O. Sars in 1877 

 and 1879 has been divided by Czerniavsky, Norman, Sars (in his later writings) and some 

 other authors: Macromysis White, Pratcmcs Leach i= Kesslerella Czern. and Synmysis Czern., 

 partim), ScJiistomysis Norm. [Austromysis Czern. and Synmysis Czern., partim), Neomysis Czern., 

 Diamysis Czern., Dasymysis Holt & Beaum. {^A cant homy sis Czern.), Michtheimysis Norm., 

 Antarctomysis Coutiere, Potamomysis Czern., Paramysis Czern., Mesomysis Czern., Limnomysis 

 Czern., Metamysis G. O. S., Caspiomysis G. O. S., and Euxinotnysis Czern. The value of many 

 of these genera is but small. 



Of animals belonging to this tribe the "Siboga" collection contains only a single specimen, 

 an adult male, and it is even necessary to establish a new genus for its reception. 



SIBOGA-EXPEDITIE XXXVII. 10 



