54 



CRUSTACEA MALACOSTRACA. III. 



Remarks. This new genus occupies a very isolated position. The mouth-parts are in the main 

 as in the lamra-group, the general outline of the body somewhat resembling that in Echinopleura (of 

 the Desmosomatini), the first pair of legs feeble, not prehensile and without spines, the other legs 

 nearly as in Pleurogonium, the male operculum uncommonly large. 



Only one species is known. 



33. Schistosoma ramosum n. sp. 

 (PI. IV, figs.4a-.4i). 



Male. Body a little more than three times as long as broad. — Anteunulce a little longer 

 than the sum of the head and the two anterior segments; first joint (fig. 4 c) twice as long as broad 

 and as long as second joint; flagellum a little longer than the peduncle, 8-jointed. The eight pairs of 

 thoracic protuberances are all somewhat long, with a single small seta or two short setse at the end; 

 fourth pair considerably longer and thicker than the fifth. — The abdominal shield almost half as 

 long again as broad; the posterior margin between the insertions of the uropods considerably convex. 

 The uropods less than one-fourth as long as the last abdominal segment; first joint is short, second 

 a little thicker and clavate, thicker beyond the middle than at the base. Each pleopod of first pair 

 with an incision in the distal end. 



Length of the single specimen 1-4 mm. 



Remarks. As it was impossible as to a number of features to separate the generic from the 

 specific characters, most of them have been mentioned in the description of the genus. 



Occurrence. Taken by the "Ingolf" at a single station. 



South of Iceland: Stat. 64: Lat. 62°o6' N., Long. ic/W W., 1041 fath., temp. 3-1°; 1 spec. 



Group V. Ischnomesini. 



Body somewhat or extremely narrow, generally most narrow at the middle, which is round. 

 Head deeply immerged within first thoracic segment and so completely fused with it that only a 

 more or less distinct, curved dorsal impression is seen as the limit, excepting frequently at the lateral 

 margin, where a sharp suture is found. Eyes wanting. Antennulae with first joint thick, nearly globular, 

 and second joint proportionately rather long or extremely long. Antennae without squama, long or 

 very long. Mandibles without palp, but otherwise in the main similar to those in the /<w/ra-group, 

 having the molar process thick, subcylindrical, transversely truncate and directed a little forwards, or 

 being vertical on the corpus mandibular — Thorax very peculiarly shaped, as fourth segment is pro- 

 duced somewhat or much backwards, fifth segment much to extremely much forwards, so that the 

 distance between the insertions of the fourth and the fifth pair of legs is from very to exceedingly 

 long; the produced parts of these segments are considerably, or very much, narrower than their leg- 

 bearing parts. First pair of thoracic legs prehensile, similar in both sexes; fifth joint with two or three 

 spines; the six other pairs slender, moderately or very long; fourth and fifth pairs subequal in length, 



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