296 U.S. NATIONAL MUSEUM BULLETIN 23 6 



Back slightly curved, with distinct depression opposite oral aperture; 

 sides greatly produced and rounded; oral field gi-eatly protruding 

 (fig. 116&). Rostrum separated from cephalic somite by shallow 

 groove, placed in depressed part of cephalic somite, triangular, shorter 

 than in preceding form, and reaching slightly beyond articulation 

 between 1st and 2nd antennular segments (fig. 117a). Apical part 

 laterally incised and provided with small hair on each side. Rostrum 

 curving slightly downward, apex blunt. 



The proportions of the various somites can best be taken from figure 

 116a. The 5th thoracic somite is remarkable by the presence, on each 

 side, of an inwardly produced, highly chitinized trabecle. The fusion 

 between 1st and 2nd abdominal somites is very incomplete and par- 

 ticularly is marked by the teeth bordering the distal ends of the somites 

 (see below). 1st abdominal somite with internal, chitinous ridge, 

 running transversally in proximal part of that somite and distinctly 

 visible in dorsal aspect. All somites, with exception of anal somite, 

 distally bordered by scale-shaped teeth. Along the cephalic somite 

 these teeth occur only in the lateral parts of the body; on the abdom- 

 inal somites the rows of teeth are interrupted ventrally. In 

 lateral aspect the armature of the genital plates (leg 6) and the seta on 

 the 3rd abdominal somite are clearly visible. 



Anal somite slightly longer than broad (proportion 7:5), anal 

 flap distinct, bordered with fine teeth, which also line insertion of furcal 

 rami (fig. 115g). Whole integument, with exception of furcal rami, 

 with curious pitted structure. On the cephalic somite the pits are 

 circular structures, ordered in regular fields. On the remaining 

 somites there are apparently short hairs, each placed on a small 

 elevation of the cuticle. In the figures this very characteristic struc- 

 ture has been represented for only a part of the anal somite. 



On each side of the anal somite, originating at the insertion of the 

 anal plate, there is a backwardly directed carina, set with fine teeth 

 and caudally terminating in a slightly produced, strongly denticulated 

 flap, covering a small portion of each furcal ramus. 



Furcal rami slightly longer than broad (proportion 5:4), slightly 

 diverging, external margin smooth, internal margin with fairly broad 

 lamella, of which the edge is strongly denticulated, 7-9 strong teeth 

 being present. There are on each ramus 3 marginal setae and 1 

 appendicular seta. Apical seta strongly thickened and lengthened; 

 2 setae are placed along external border, while appendicular seta 

 inserts at base of a low carina, running longitudinally across each 

 ramus, which carries a few caudal spinules. 



Antennules (fig. 117a) short, % length of cephalic somite, 4-seg- 

 mented, segment 2 with strong, externally directed spine. Segment 3 

 fairly long, with short conical process carrying aesthetasc and 2 setae. 



