174 U.S. NATIONAL MUSEUM BULLETIN 236 



5 strong, nude spiniform setae inserting along spinulose border of 

 baso-endopodite. 



This specimen agrees with Norman and T. Scott's description of 

 Megarthrum purpurocinctum (1906, p. 175) except for the following 

 points: 



1. Norman and T. Scott's specimen measured 0.5 mm., but the 

 specimen here is smaller (0.30 mm.). 



2. Spine and seta on 2nd endopodal segment of leg 1 are very short 

 in Norman and T. Scott's drawing (pi. 14, no. 9) but they may have 

 been drawn from a slightly oblique position of the segment. 



3. The spines at the baso-endopodite appear to have been plumose 

 in Norman and T. Scott's specimen (pi. 20, fig. 4); here they are 

 long and nude. 



4. The curious color pattern is completely faded in the present 

 specimen. 



The specimen from locality 431 is strongly contracted and curved; 

 it shows the color pattern characteristic for this species as well as 

 some additional structural particularities; its external appearance 

 is described below (fig. 62c). 



Adult female (loc. 431), 0.27 mm.; greatest diameter 0.14 mm. 

 Cephalic somite, composed of fused head and 1st thoracic somite, 

 anteriorly broadly rounded, almost semicircular, posteriorly concave. 

 Posterolateral parts shghtly produced. Epimeral plates of 2nd to 

 5th thoracic somites well developed, produced caudally, and well 

 visible in dorsal aspect; caudally they increase in size. Even on 

 the 5th thoracic somite there are well-developed epimeral plates, 

 reaching as far as % the genital somite. They also cover the antero- 

 lateral parts of that somite. Cephalothorax remarkable further by 

 development of small, chitinized ridges on walls of somites, visible 

 along distal walls of cephalon and 1st thoracic somite. These 

 chitinized ridges in reality are placed on the anterior part of the 

 following somite (2nd and 3rd thoracic somites) and are covered by 

 the posterior free part of the preceding somite in the stretched animal. 

 The ridges are visible here because of the strongly curved body. 

 They form a very prominent structural feature, they are visible in 

 Sewell's figure 29a (1940) but they are not mentioned in his text. 

 Neither are they visible in Norman and T. Scott's figures nor are 

 they mentioned in the text. 



Abdomen as in previous specimen, but genital somite slightly 

 shorter and line of fusion less visible. Spinules on genital somite on 

 sides near line of fusion and along distal border. Similar spinules 

 on 3rd and 4th abdominal somites. Anal somite and furca as in 

 previous female specimen, but furcal setae damaged. The color, 



