146 U.S. NATIONAL MUSEUM BULLETIN 236 



Atlantic, penetrating even into Arctic seas. The distribution in the 

 Atlantic is summarized by Sewell (1940, p. 236) and is given exten- 

 sively by Lang (194S, p. 530); it occurs along American and European 

 coasts from Franz Joseph Land to Madeira and the Canary Islands. 

 The only Pacific record available is Addu Atoll in the Maldive Archi- 

 pelago (Sewell, 1940), where a single specimen (no sex and length 

 given) was found in weed washings. At Ifaluk a single specimen 

 occurred in a sand sample, taken some 100 feet from the reef margin. 



Genus Dactylopusia Norman, 1903 



Dactylopusia tisboides (Claus, 1863) 



Figures 53-55 



Dactylopus tisboides Claus, 1863, p. 127, pi. 16 (figs. 24-28). — Klie, 1949, p. 122. 



Dactylopiisia tisboides.— Vktoyei, 1928, p. 182.— Marine Biological Association, 

 1931, p. 162.— Eraser, 1936, pp. 25, 26.— Nicholls, 1939, p. 256.— Sewell, 

 1940, pp. 127, 222, 352, 353, 357, 361, 363, 366, 367, 369, 370, 373-376.— 

 Nicholls, 1941b, p. 71; 1944a, p. 489; 1945, p. 1.— Gaspers, 1951, p. 66.— 

 Gallingani, 1952, p. 75. — Marine Biological Association, 1957, p. 166. 



Dactylopodia tisboides. — Lang, 1944, p. 13. — Dahl, 1948, p. 95. — Lang, 1948, p. 

 545, figs. 222 (no. 1), 223 (no. 1).— Noodt, 1955a, p. 203.— Maghraby and 

 Perkins, 1956, p. 491.— Roe, 1958, p. 228.— Wieser, 1959, p. 107.— Roe, 

 1960, p. 279. 



Material.— Log. 425, 1 ad. 9, 0.38 mm.; 2 ad. cf d", 0.38 and 0.39 

 mm. Loc. 431, 1 ad. cf, 0.35 mm. Loc. 590, 1 ad. 9, 0.39 mm. 

 Loc. 638, 1 ad. cf, 0.38 mm. 



Description. — The following is based on the female specimen 

 from locality 590 and a male specimen of 0.39 mm. length from locality 

 425; in addition, a female specimen from locality 425 has been used. 

 All specimens have been dissected and the appendages mounted. 



Adult female, total length 0.39 mm.; greatest diameter 0.14 mm.; 

 length of longest furcal seta 0.38 mm. 



Body strongly built, compact, with ovoid cephalothorax and short 

 abdomen (proportion 9:4). Greatest diameter of cephalothorax at 

 end of cephalic somite, broadly rounded anteriorly, gradually nar- 

 rowing posteriorly, not sharply separated from abdomen, particularly 

 in contracted specimens without sharp delimitation between these 

 two regions of the body (figs. 536, 54a). Head and 1st thoracic 

 somite fused to form cephalic somite, which is longer than combined 

 lengths of thoracic somites 2 to 4. Line of back, in lateral view, 

 broadly rounded and curving without interruption into rostrum. In 

 dorsal view, rostrum separated from cephalic somite by shallow groove. 

 Rostrum a small, triangular structure with rounded apex, as long as 

 1st antennular segment. Lateral parts of cephalic somite slightly 

 produced to cover basal parts of oral appendages, laterocaudally 



