170 U.S. NATIONAL MUSEUM BULLETIN 236 



4. Internal seta 1st segment of endopodite leg 1 inserting halfway along margin. 



I. forficata Philippi 



Internal seta 1st segment of endopodite leg 1 inserting in proximal third of 



internal margin I. scotti Lang 



Idomene purpurocincta (Norman and T. Scott, 1905) 



Figures 62, 63 

 Dactylopusia purpurocincta Norman and T. Scott, 1905, p. 295. — Lang, 1936c, 



p. 30. 

 Megarthrum purpurocinctum. — Norman and T. Scott, 1906, p. 175, pis. 10 (fig. 



17), 12 (fig. 10), 13 (fig. 10), 14 (fig. 9), 18 (fig. 6), 19 (fig. 1), 20 (figs. 4, 5).— 



Marine Biological Association, 1931, p. 163; 1957, p. 167. 

 Idomene purpurocincta. — Lang, 1936c, pp. 26, 30; 1948, p. 569, figs. 231 (no. 8), 



233 (no. 2). 

 Xouthous purpurocinctum. — Sewell, 1940, pp. 197, 357, 371, fig. 29. 



Material. — Loc. 425, 1 ad. 9, 0.30 mm. Loc. 431, 1 ad. 9, 0.27 

 mm. 



Description. — The female specimen from locality 425 has been 

 described completely and has been dissected and mounted. The ex- 

 ternal appearance of the female from locality 431 is also described; 

 this specimen has been preserved. 



Adult female (from locality 425), total length 0.30 mm.; greatest 

 diameter 0.14 mm.; length of longest f ureal seta 0.11 mm. 



Body strongly built and of characteristic appearance, with broadly 

 rounded front, gradually tapering posteriorly, compressed dorso- 

 ventrally and with short f ureal setae (fig. Q2a). Head and 1st tho- 

 racic somite completely fused to form cephalic somite, which is as 

 long as combined lengths of thoracic somites 2 to 4. Line of back 

 in lateral aspect smoothly curved, gently running into small rostrum 

 (fig. 626). Laterally it is scarcely produced, but the laterocaudal 

 border is slightly drawn out. Cephalic somite in dorsal aspect ante- 

 riorly very broadly rounded, almost semicircular, caudally concave. 

 Rostrum invisible from above, small, bluntly pointed, as long as 1st 

 antennular segment. Greatest diameter of body at oral aperture. 

 Thoracic somites 2 to 4 of nearly same length; epimeral plates con- 

 siderably produced backward, increasing in length caudally, with 

 the result that epimeral plate of 4th thoracic somite reaches halfway 

 along genital somite. 5th thoracic somite small, without epimeral 

 plates, visible both dorsally and laterally. No teeth visible on tho- 

 racic somites. 



Genital somite resulting from fusion of abdominal somites 1 and 2; 

 line of fusion visible both laterally and dorsally. Genital somite 

 barrel-shaped in dorsal view, more than 2 times as wide as long, 1% 

 times as long as 3rd abdominal somite. 4th abdominal somite slightly 

 shorter than 3rd, as long as anal somite. Spinules occur on latero- 

 ventral surfaces of genital, 3rd, and 4th somites. Anal somite with 



