46 



are spirally twisted as in most species of Siriella, while the endopods and exopods of third or 

 fourth pairs are completely similar, without thickened setae. 



This sharply defined new genus comprises two new species, both captured by the "Siboga". 



Key to the Species. 



Endopod of uropods at most as long as, or conspicuously shorter than, 



the exopod H. pulchra n. sp. 



Endopod of uropods reaches conspicuously beyond the end of the exopod. H. parva n. sp. 



25. Hemisiriella pulchra n. sp. PI. V, figs. 50—5^; PI. VI, figs. \a — \p. 



Stat. ij. March 30/31. Sailus ketjil, Paternoster-islands. Plankton, surface. Large number of 



specimens. 

 Stat. 41. April 3. Lat. 7°25'S., long. ii7°5o'.5E. 9601. Plankton, 10 m. to surface. Large 



number of specimens. 

 Stat. 43. April 4/5. Anchorage off Pulu Sarassa, Postillon-islancls. Depth up to 36 m. HENSEN 



vertical net with electric light. 1 specimen. 

 Stat. 75. June 8. Lat. 4°57'.4S., long. ii9°2.8E. 18111. HENSEN vertical net with electric 



light, from 1 1 m. to surface. 1 specimen. 

 Stat. 125. July 18/19. Anchorage off Sawan, Siau-island. Plankton. 1 specimen. 

 Stat. 148. August 10. Lat. o° 17.6 S., long. I29°I4'.5E. 1855 m. Hensen vertical net, from 



1000 m. depth to surface. 3 large specimens. 



Description. - Slender. Frontal plate somewhat produced (PI. V, fig. $a) forming 

 a moderately low triangle with the apex acute and sometimes feebly acuminated. Eyes of very 

 moderate size, red. Antennal squama (PI. VI, fig. ir) somewhat less than three times as long 

 as broad; terminal lobe much broader than long. Uropods moderately broad, subsimilar in both 

 sexes (PI. VI, figs. 1 n and 10); endopod at most as long as, and generally conspicuously shorter 

 than, the exopod; exopod with 5 — 8 spines occupying at most scarcely one-third of the outer 

 margin of the proximal joint, its distal joint somewhat less than twice as long as broad. Telson 

 (PI. VI, fig. 1 n) proportionately short, not reaching the articulation of the exopod, only a little 

 more than twice as long as broad and similar in both sexes ; the proximal part is very widened, 

 with two pairs of marginal spines; from the proximal pair of these spines the telson narrows 

 rather quickly, and then the margins are parallel to slightly beyond the middle, where the 

 spinulation begins, wherefrom they gradually converge more to the broadly rounded end; the 

 lateral spines on this distal part (fig. ip) are comparatively few in number, only about 8 or 9, 

 the more proximal ones irregular as to size and intervals, while the distal four pairs increase 

 rapidly in length posteriorly; the end has 3 small spines and a couple of long setae at the 

 middle, more laterally 2 pairs of long spines, the outer pair conspicuously longer than the inner. 



Length of a large male 9.3 mm., of a large female 9 mm. 



H. pulchra var. vel n. sp.? 



Stat. 142. August 5/7. Anchorage off Laiwui, coast of Obi Major. 23 m. Hensen vertical net 

 with electric light. 1 specimen. 



