PERCY SLADEN TRUST EXPEDITION. 
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Genus COLOMASTIX, Grube, 1861. 
15. Colomastix crassimanus (Heller). 
III. Suakim Harbour: sponges. One ¢, one @. 
Length of ¢ 5mm., 2 4mm. 
This form has hitherto been regarded as the adult male of C. puséllus, Grube, because 
the female agrees with that species. As, however, it has never been recorded from 
the British area, where C. pusillus is not uncommon, or from the Atlantic coast of 
France, it is probable that these species (like Seba &c.) differ only in the males, and I 
have therefore revived Heller’s name. The sexual differences are not confined to 
gnathopod 2: in the male the joints of all the perzeopods are swollen, gnathopod 1 is 
atrophied (Della Valle) or wanting (Heller); the outer ramus of uropod 1 is peculiarly 
formed and the inner ramus of uropod 3 very wide. In the above specimen the palm 
of gnathopod 2 has only two teeth instead of 3 as figured by Heller and Della Valle, but 
this isa variable character ; the 6th joints of the pereeopods are pyriform and smooth, and 
the dactyli very small. C. hamifer, Kossmann, is probably identical with the above, as 
the palmar teeth of gnathopod 2 are difficult to see. 
Genus SYNOPIA, Dana, 1852. 
16. Synopia scheeleana, Bovallius. 
I. Salomon Atoll, Q, seven. Cargados,g. Amirante, gg. Surface Plankton. 
Length 3-4 mm. 
Genus STENOPLEURA, Stebbing, 1888. 
17. Stenopleura atlantica, Stebbing. 
1. N. of Chagos, B, 50 fms.: one. N-.E. Gt. Chagos Bank, L, 125 fms.: one young. 
8. by E. of Farquhar, s, 500-750 fms.: one ¢, length 5 mm. N.W. of Desroches, 
kk, 150 fms.: one. All Plankton. 
Perzeopod 5 (broken in the ‘ Challenger’ specimen) is much longer than per. 4. 
Genus CHAGOSIA, gen. n. 
Body rather broad. 
Head much deeper than the body, buccal mass and maxillipeds prominent. 
Side plates not as deep as the segments. 
Antenna 1 much shorter than ant. 2; peduncle short ; flagellum long and tapering. 
Gnathopods with narrow, subchelate, 6th joints; gnath. 2 resembling but longer 
than 1. 
Uropod 3 uniramous. 
Telson long, deeply notched, the divisions dehiscent. 
This genus, represented by a single specimen, is provisionally placed under Calliopiide, 
with which, so far as can be judged without dissection, it has the most affinity. 
