280 U.S. NATIONAL MUSEUM BULLETIN 23 6 



Description. — The following is based on the adult female (loc. 

 592), which has been dissected and mounted. Some notes on the 

 two remaining specimens, which are preserved as whole mounts, are 

 included here. 



Adult female, total length 0.62 mm.; greatest diameter 0.14 mm.; 

 length of longest furcal seta 0.18 mm. 



General shape of body comparatively slender, with greatest diam- 

 eter in oral region; anteriorly more or less rounded, posteriorly 

 gradually narrowing, in dorsal view of very characteristic appearance. 

 In dorsal aspect division between cephalothorax and abdomen scarcely 

 visible, in lateral view marked by strong curvature of body (fig. 112d). 

 Head and 1st thoracic somite completely fused to form cephalic 

 somite, which in length slightly exceeds thoracic somites 2 to 4 

 combined. Sides of cephalic somite slightly angularly produced, 

 covering basal parts of oral appendages; oral field greatly produced 

 and protruding. Extreme anterior part of cephalic somite, between 

 antennules, obtuse; rostrum small; integument of cephalic somite, as 

 appears from lateral view, curves inward to form short plate, medially 

 broadly incised to form 2 blunt points (fig. 114a). Thoracic somites 

 2 to 4 of equal length, epimeral plates well produced, rounded. Some 

 spinules occur along distal border of thoracic somite 4. 



5th thoracic somite distinctly visible, especially traceable by big 

 5th feet, distally with some dorsal spinules. Genital somite composed 

 of more or less fused abdominal somites 1 and 2; line of fusion very 

 distinct dorsally and laterally. Abdominal somites 1 to 3 of nearly 

 same length; somite 4 and anal somite shorter. Anal somite twice as 

 broad as long, anal flap broadly rounded. Furcal rami very long and 

 slender, half length of abdomen, 4 times as long as anal somite and 

 7 times greatest diameter. Some small spinules on anal somite near 

 insertion of furcal rami. Kami diverging slightly, each slightly but 

 distinctly sigmoid, and at same time narrowing from base to apex, 

 internally haired (fig. 112/). Each ramus has 5 marginal setae and 1 

 appendicular seta. Setae 1, 3, 4, 5, and appendicular seta of equal 

 length, short. Seta 1 at end of internal border; setae 4 and 5 at K 

 and % of external border, seta 3 at end of external border. Seta 2 

 greatly lengthened and thickened, not swollen at base. 



Antennules (fig. 113/) short, about as long as cephalic somite, 9- 

 segmented; jointing between segments 7 and 8 indistinct, with the 

 result that they can easily pass as 8-segmented. Segment 1 lengthened, 

 about 4 tunes as long as broad. 2nd segment with large, externally 

 directed spur. Segment 4 with conical process, carrying aesthetasc 

 and 2 setae. Setation represented in figure 113/. 



Antenna (fig. 113^) with basis and 1st endopodal segment separate. 

 Basis long and slender. Exopodite styliform, 1-segmented, with 3 



