56 



with the lobe from second joint small; no lobe from third or fourth joint; a spiniform terminal 

 claw cannot be distinguished among some other spines. Gnathopods with the claw somewhat 

 loner, very obvious. Six pairs of thoracic legs in some species with a distinct, terminal, slender, 

 longer or shorter claw (PI. VIII, fig. 2g), while in other forms a claw seems to be wanting. 

 In the male first and second pairs of pleopods always biramous, but the rami of second pair 

 very different in various species; third pair with the exopod very or extremely elongated, while 

 the endopod is sometimes well developed, sometimes rudimentary, sometimes proximally coalesced 

 with the exopod or not marked off from the peduncle (in the latter case really existing ?) ; 

 fourth and fifth pairs small, generally with both rami very conspicuous, but in one species 

 {G. parims m.) with the exopod quite rudimentary. 



Remarks. — Several of the species are closely allied; the two species captured by 

 the "Siboga" are in reality so similar to each other that the females may be far from easy to 

 separate, while the male pleopods show most striking differences. If the differences in the male 

 pleopods should be used in the same degree as has been done by various authors as to some 

 other groups of the Mysidse, the genus Gasfrosacais ought to be divided into at least three 

 genera, but judging from the great conformity in most or sometimes in all other particulars, 

 I think such splitting to be far from natural. The result is that I cancel the genus Haplostylus 

 Kossmann based on the reduction or absence of the lobes on the carapace and on the reduction 

 (not absence) of the endopod of the third pair of male pleopods. The genus Chlamydopleon Ortm. 

 has been imperfectly described, but Ortmanx's type of the genus is a species certainly closely 

 allied to Gastrosacctis spinifer Goes. 



30. Gastrosacctis indicics n. sp. PL VIII, figs. 2a — 2 r. 



Stat. 16. March 1516. Lat. 6° 59' S., long. 115° 24.7 E. Bay of Kankamaraan, S. coast of 



Kangeang. 22 m. Hensen vertical net, with electric light. About 20 specimens. 

 Stat. 37. March 3031. Sailus ketjil, Paternoster-islands. 27 m. and less. Plankton, surface. 



I specimen. 

 Stat. 41. April 3. Lat. 7° 25' S., long, i 17° 50'. 5 E. 96 m. Plankton, 10 m. to surface. 2 specimens. 

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



8 — 10 m. Plankton. 6 specimens. 

 Stat. 99. June 28;29;30. Lat. 6°7'.5 N., long. 120° 26' E. Anchorage oft" North-Ubian. 16 — 23 m. 



Plankton, surface, i specimen. 

 Stat. 109. July 5;'6. Anchorage off Pulu-Tongkil, Sulu- Archipelago. Plankton, townet. i specimen. 

 Stat. 125. July 18 19. Anchorage off Sawan, Siau-island. 27 m. Plankton, townet. i specimen. 

 Stat. 148. August 10. Lat. 0° I7'.6 S., long. I29°I4'.5E. Hensen vertical net, from looo m. 



depth to surface, i specimen. 



Description. — Closely allied to G. Normani G. O. Sars. Carapace with a short 

 or very short, triangular or distally more rounded frontal plate (figs. 21a: — 2b): no trace of 

 free lobes at the posterior margin. Eyes somewhat small, very much broader than long and 

 about as broad as the eye-stalks, which are very short, twice or more than twice as broad as 

 long above a little nearer the outer than the inner margin. Antennulse with the first peduncular 

 joint decidedly longer than the sum of the two following joints. The antennal squama (fig. 2 c) 



