is uncommonlv simple; the furrow between the last and the penultimate thoracic segment is 

 quite free, deep, and curved a little forwards; there are no protuberances between the coxse 

 and no plate, but the transverse somewhat narrow area, marked off posteriorly by the furrow 

 and anteriorlv by the limit between fourth and third segment running between the posterior 

 part of third coxse, is very convex in the longitudinal direction. 



Length of a large specimen 20.5 mm.; the type for fig. 4/ is 15.5 mm. long. 



Remarks. — The male A. serndatus is easily distinguished from all other forms by 

 the triano-ular protuberance from the upper end of first joint in the main "branch" of the lower 

 antennular flagellum ; the reduced and curiously shaped petasma affords another fine character. 

 The female is distinguished by the genital area. — It may be noted that in the female from 

 the Indo-Chinese Sea the front crest on the carapace has only a single dorsal denticle, the 

 posterior, as the anterior denticle, which is small in normal specimens, has vanished. 



6. Acetes spiniger n. sp. PI. IV, figs. 5« — 5/2. 



Not captured by the "Siboga", but the Copenhagen Museum possesses specimens from 

 3 localities, one among them within the "Siboga" area. 



Surabaya, Java. Capt. Andréa 1870. 6 females. 



10 miles off Rangoon. HANSEN & THALBITZER. About 35 specimens. 



u Indo-Chinese Sea". ScHMIDT. I male, 2 females. 



Male. — Transverse diameter of the eyes a little less than half as long as the distal 

 joint of the stalk with eye. Antennulae (fig. 5 a) with second joint a little elongated and some- 

 what thickened; third joint very elongated, from a little more than twice to a little less than • 

 three times as long as the inner margin of second joint, and 'when this joint is extremely long 

 it is proportionately more slender than when it is only a little more than twice as long as the 

 margin mentioned. Thickened part of the upper flagellum considerably shorter than the inner 

 margin of second peduncular joint. Lower flagellum (fig. 5 c) considerably longer than second 

 peduncular joint, with 12 distinct joints; the shaft is long, one-third of the whole flagellum, 

 3-jointed, and third joint with the end a little produced, free; first joint of the main "branch" 

 long, in reality consisting of two joints completely or — in a single male - - somewhat incom- 

 pletely fused; the four proximal joints of the main "branch" taken together feebly curved, 

 compressed and somewhat high, highest at the middle; second and third joints each with a 

 moderately long spine below, and fourth joint with a row of 6 or 7 spines, the distal ones 

 short (in the large male from the Indo-Chinese Sea first joint has a spine below, the spines on 

 the three other joints are longer, and fourth joint has 8 spines). Third joint of the shaft has 

 above at the middle a somewhat small, spiniform, curved process looking mainly forwards, and 

 its end has the usual extremely long, thick spine, the submedian part of which is much curved, 

 and the spine reaches to the spines on fourth joint of the main "branch"; before the insertion 

 of the very long spine a short, straight spine originates near the end of the upper margin of 

 the joint. Antennal squama reaches to or slightly beyond the end of second antennular joint. 

 Coxae of third pair of legs (fig. 52) with a good-sized tooth at the distal inner angle; the 



