. 39 



ventralis two gigantic hooks are seen on the front side (fig. 4//), and at the end of the narrow 

 part two or three minute hooks are seen on both sides. 



Length 15.7 mm. 



Female. — Similar to the male excepting in the antennula;, the coxa; of third pair 

 of lees, and the genital area. The peduncles of the antennulae as in the female A. vzils-aris, so 

 that a reference to the description is sufficient; lower flagellum consists of about 14 joints, and 

 it is almost as long as the two distal peduncular joints combined. Coxse of third pair of legs 

 with the inner side nearly as in the female A. vjt/garis, having at the distal end a strong 

 tooth (fig. 4^?), the inner margin concave and the produced rounded small plate at the base; 

 trochanter with the produced inner end sometimes close to next joint, sometimes turned a little 

 outwards and then seen as a free acute angle or minute tooth, but no tooth is, as in A. spi- 

 niger^ found on the inner side just before the end. 



The genital area (fig. \e) differs from that in A. vtdgaris\ there is no trace of protuber- 

 ances between the coxse of third legs; the deep transverse furrow is sinuate, having its sub- 

 lateral parts procurved and the median part recurved. Between the coxse and the furrow the 

 median third of the lower surface has an elevated area which has its raised lateral margins 

 somewhat convergent, while the posterior margin is bent a little backwards at the middle, 

 and each half is a little concave or frequently straight (fig. \c shows the area in its most 

 developed form). 



Length 21.7 mm. 



Remarks. — A. Siboga is more allied to A. vtilgaris than to any of the following 

 species; its male differ from A. vulgaris especially in the long third joint of the antennulae, 

 in having no distal tooth on the coxse of third legs, and in the capitulum of the petasma, 

 while the males of the following^ forms diifer from those of A. vuio^aris and A. Sibos^a in having- 

 the genital coxse broadly rounded anteriorly and no pars astringens on the petasma. 



3. Acetes dispar n. sp. PI. Ill, figs. 5 a — 5/ and PI. IV, fig. \a. 



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

 two localities, one of which is within the "Siboga" area. 



Cheribon, Java. Capt. Andrea 1870. i male, 4 females. 



Lem Ngob, Gulf of Siam, in a mangrove-swamp. Dr. Tn. MoRTENSEN 23/XII 1899. 2 males 

 and I immature specimen. 



Male. — Transverse diameter of the eye (fig. ^d) only about half as long as the distal 

 joint of the stalk with eye. In the antennular peduncles second joint is half as long as the 

 first; third joint is slender and very elongated, more than two and a half times as long as 

 the inner margin of second joint; thickened part of the upper flagellum somewhat shorter than 

 the inner margin of second peduncular joint. Lower flagellum a little longer than the inner 

 margin of second peduncular joint, with 13 joints; the shaft of the clasping organ (fig. 5^) is 

 proportionately longer than in A. vulgaris^ 3-jointed with first joint long; the main "branch" 

 has 10 joints, the proximal part is considerably curved with 2 or 3 small spines on fifth joint. 



