COPEPODA FROM IFALUK ATOLL 233 



Specimens of Amphiascoides subdebilis occur in the Ifaluk collection. 



Amphiascoides subdebilis (Willey, 1935) 



Figures 92a,6, 93, 94 



Amphiascus subdebilis Willey, 1935, p. 64, figs. 49-52.— NichoUs, 1939, p. 265.— 



Sewell, 1940, p. 266. 

 Amphiascoides subdebilis. — Nicholls, 1941, p. 415; 1941b, pp. 81, 82. — Klie, 1950, 



p. 85.— Noodt, 1955a, p. 207. 

 Amphiascella subdebilis. — Nicholls, 1939, p. 265. — Lang, 1948, p. 718, fig. 290. — 



Roe, 1960, p. 283. 

 Amphiascus subdebilis var. intermixlus Willey, 1935, pp. 64, 65, fig. 48. 

 Amphiascus intermixtus. — Nicholls, 1941, p. 415, fig. 18; 1941b, pp. 81, 82. 

 Amphiascus debilis Monard, 1928, p. 390, fig. 32 (no. 3); 1935a, p. 31; 1937, p. 



43. 

 Amphiascus debilis pp. Monard 1928a, pp. 381, 383. — Pesta, 1932, p. 63. 



Material.— Loc. 589, 2 ov. 99, 0.42 and 0.50 mm. Loc. 592, 1 

 ad. 9, 0.45 mm., 1 ov, 9, 0.54 mm. Loc. 800, 1 ad. 9, 0.42 mm. 



Description. — The material of this form falls into two different 

 groups, 0.42-0.45 mm. and 0.50-0.54 mm. long respectively, which 

 are slightly different in the external appearance and setation of leg 

 5. Both will be described. 



Adult female (loc. 592), total length 0.54 mm.; greatest diameter 

 0.14 mm.; length of longest furcal seta 0.27 mm.; proportional length 

 of cephalothorax and abdomen is 1:1. 



General shape of body slender, with greatest diameter at middle of 

 cephalic somite, anteriorly and posteriorly narrowing, without sharp 

 demarcation between cephalothorax and abdomen, but division 

 visible by slight lateral expansion of 5th thoracic somite (fig. 92a). 

 Head and 1st thoracic somite completely fused to form cephalic 

 somite, which is slightly longer than combined lengths of thoracic 

 somites 2 to 4. Back gently curved and running into rostrum; 

 sides of cephalic somite only slightly produced to cover extreme basal 

 portion of oral appendages (fig. 926). Rostrum short, triangular with 

 rounded apex, base broad, cm-ved forward and downward, separated 

 from cephalic somite by shallow groove, as long as antennular seg- 

 ments 1 and 2. Ventrolateral parts of cephalic somite not produced. 

 Epimeral plates of thoracic somites 2 to 4 rounded and slightly 

 back war dly produced. 



5th thoracic somite distinctly visible laterally and dorsally; in 

 dorsal aspect slightly laterally produced. Genital somite resulting 

 from fusion of abdominal somites 1 and 2, line of fusion visible 

 dorsallj^ and laterally, broader than long (proportion 9:7), slightly 

 shorter than combined lengths of abdominal somites 3 and 4. There 

 are no spinules on the abdominal somites. Anal somite shorter than 



