35 



Description. — Moderately slender. Frontal plate in both sexes somewhat produced 

 (fig. 2rt), narrowly triangular, with the tip nearly or completely acute. Upper side of the 

 carapace without any protuberance. Eyes of very moderate size, generally reddish, sometimes 

 dark or nearly black with somewhat or very feebly reddish tint. Antennular peduncles in the 

 male moderately thick. Antennal squama a little narrower in the male (fig. 2 d) than in the 

 female (fig. 2 c), from a little less to a little more than three times as long as broad, with its 

 distal lobe somewhat varying in shape, but always unusually long, from at least two-thirds as 

 long as broad to a little longer than broad. Gnathopods (fig. 2e) and thoracic legs moderately 

 robust ; first pair of thoracic legs slightly shorter than third ; sixth joint of the legs divided by 

 a distinct articulation. Male pleopods and pseudobranchial rami (fig. 20-) as described in the 

 definition of the group. 



Uropods a little more slender in the male (fig. 2 k) than in the female (fig. 2 //) ; exopod 

 as long as, or a little longer than, the endopod, with from 3 to 9, but generally with 5 to 7, 

 spines occupying less than one-third of the margin of the proximal joint, while the distal joint 

 is from slightly more than half as long again to nearly twice as long as broad. The telson 

 (fig. 2 /i) reaches somewhat behind the articulation of the exopod, it is slightly narrower and a 

 little longer in the male than in the female, between two and a half and three times as long 

 as broad ; the widened basal part has two pairs of spines ; the small spines occupy more than 

 half of the lateral margins, and along nearly the distal third of the margins these spines are 

 regularly arranged and increase quite regularly (fig. 2 i) in length to the end ; the terminal pair 

 of long spines are about twice as long as the most distal lateral spines and frequently more 

 than twice as long as the three spines between them. 



Length 6.5 to y.'j mm.; the males generally a little longer than the females. 



Remarks. — According to the stations this species is very common near the shores 

 in a large part of the area explored by the "Siboga". It is easily distinguished from all other 

 species by the shape of the antennal squama taken together with the regular spinulation of 

 the distal third of the telson ; in the latter feature it is more related to S. nodosa m. and S. 

 affinis m. than to any other form. 



Considering the variation mentioned in the colour of the eyes and the number of spines 

 on the exopod of the uropods, one might suppose that 5. vulgaris comprises two or three species, 

 and judging from the fact that S. media n. sp. can scarcely be separated from S. inornata n. sp. or 

 S. conformalis n. sp. from 5. distingiienda n. sp. without the aid of the secondary development 

 of spines on the fourth pair of male pleopods, it may in reality be possible that 5". vulgaris^ in 

 which the male pleopods afford no such excellent characters, comprises more than one species. But 

 I have been unable to divide the species, and doubt whether it can be done with any certainty at all. 



A female from Stat. 36 and four females from Stat. 66 have an Epicarid in the marsupium. 



17. Siriella affinis n. sp. PI. Ill, figs. 3« — 3/. 



Stat. 66. May 7/8. Bank between islands of Bahuluwang and Tambolungan, south of Saleyer. 



8 — 10 m. Plankton. 12 specimens. 

 Stat. 106. July 5/6. Anchorage off Pulu Tongkil, Sulu Archipelago. 13 m. Plankton. 14 specimens. 



