COPEPODA FROM IFALUK ATOLL 301 



Nannomesochra arupinensis (Brian, 1925) 



Figures 116c, 119 



Mesochra arupineyisis Brian, 1923, p. 130 (nomen nudum). 



Mesochra arupinensis Brian, 1925, p. 20, figs. 8-16. 



Nannomesochra arupinensis. — Lang, 1948, p. 1189, fig. 474. — Noodt, 1953, p. 



16, figs. 37-41; 1955a, p. 212; 1957, p. 154.— Roe, 1960, p. 283. 

 Pseudomesochra parvula Gurney, 1927, p. 543, fig. 153. 

 Mesochra armoricana Monard, 1935a, p. 58, pi. 10 (fig. 144) (male only). 



Material.- — Harry Sta. 41, 1 ad. 9, 0.35 mm. 



Descriptiox. — The following is based on the only female specimen 

 available, which has been dissected and mounted. 



Adult female, total length 0.35 mm.; greatest diameter 0.12 mm.; 

 length of longest furcal seta 0.15 mm. 



Body more or less spindle-shaped, not unlike condition found in 

 Ectinosoma, with elongated, ovoid cephalothorax and cylindrical 

 abdomen; both regions of body distinctly separate (fig. 116c). Great- 

 est diameter of body at end of cephalic somite, anteriorly and poste- 

 riorly narrowing. Anterior part of body rounded and not obtuse as 

 appears in drawings of this species from Atlantic or Mediterranean 

 localities. Cephalothorax and abdomen of nearly equal length. 

 Head and 1st thoracic somite fused. Length of cephalic somite 

 equal to that of thoracic somites 2 to 4 combined. Rostrum small, 

 triangular plate with fairly broad base, visible dorsally between 

 antennular bases, and rounded apex, pointing obliquely downward 

 and forward, separated from cephalic somite by shallow groove. 

 Thoracic somites 2 to 4 of equal length, distal margins smooth. 5th 

 thoracic somite narrow, present as narrow collar at beginning of 

 abdomen. 



Abdominal somites strongly contracted in this specimen. Genital 

 somite composed of fused somites 1 and 2, IJ2 tunes as broad as long, 

 line of fusion distinctly visible dorsally. Somites 3 and 4 of equal 

 length, each % length of genital somite, distal margins smooth. 

 Anal somite shorter than either 3 or 4, anal plate invisible. Spinules 

 occur on each side of furcal insertion. Furcal rami twice as broad as 

 long, parallel, with 4 marginal setae and 1 appendicular seta. Setae 

 1, 5, and appendicular seta small and fine, seta 1 at end of internal 

 margin, seta 5 halfway along external margin. Appendicular seta 

 placed at internal distal corner of each ramus. Setae 2, 3, and 4 

 lengthened, especially 2nd and 3rd, which also have some dispersed 

 spinules. Some spinules occur on furcal rami near insertion of seta 1. 



Antennules very short, 7-segmented. Segment 2 big, with trans- 

 verse row of spinules. Segment 4 with small conical process, bearing 

 short aesthetasc and 1 seta. Setation represented in figure 119/. 



