COPEPOD GENUS RIDGEWAYIA — ^WILSON 149 



Surface of all segments and of caudal rami, both dorsally and ventrally, 

 covered by irregular groups of minute spinulose scales (not illustrated). 

 Segments with nonserrate, inconspicuous fringe; second and third 

 segments with a prominent proximal sclerotization on each side 



(fig. 1). 



In lateral view, the genital segment appearing rounded and only a 

 little produced ventrally. External portion of the genital field simple 

 (fig. 8), more or less defined by a cuticular sclerotization which is 

 heavier in the posterior area; the distal half with a crosswise, asym- 

 metrical opercular flap drawn out on the right side into a pointed 

 process; the slit formed by the flap noticeable in lateral view (fig. 2); 

 when turned semilaterally, the process of the right side prominent. 

 Paired genital openings set close together, rather large, filling most of 

 the area defined by the external sclerotization (outlines visible with 

 oil immersion objectives, but structurally indistinct). 



Caudal ramus with its inner portion somewhat expanded proximally; 

 the distal inner margin armed with fine hairs. In most specimens the 

 rami a little divergent, but parallel in some specimens and closely 

 set so that the inner expansions of the basal part cross over one another 

 (the rami thus apparently with a somewhat flexible attachment). 



Caudal setae consisting of an outer, subterminal spine shorter than 

 the ramus, and four long, plumose, terminal setae, the outer of which 

 is shorter than and the inner subequal to the urosome. The two 

 middle setae with thickened, jointed bases; both longer than the 

 urosome; the innermost of these two setae the longer, jointed second- 

 arily near its distal third and without hau's beyond this joint. A short 

 seta with very long marginal hau's inserted dorsally between the bases 

 of the innermost setae. Ventrally, two flat spinules overlying the bases 

 of the setae (fig. 7). 



Rostrum (fig. 4) of the broad form characteristic of the genus, not 

 demarcated at base, tapered to a rounded point. A pair of minute 

 frontal hairs present above the base of the rostrum. 



Antennule reaching to about the end of the metasome; comprised 

 of 26 clearly defined segments (fig. 14). The two proximal segments 

 subequal in length to one another (fig. 16), wider and longer than most 

 of the succeeding segments except the four apical segments, which are 

 progressively narrowed and lengthened (fig. 21). Two setae on every 

 segment except segments 1, 21, and 22 which have only one each, 

 segment 2 which has four setae, and segment 26 which has one lateral 

 and five terminal setae. On many segments, particularly in the 

 midportion of the antennule, the proximal seta short and hairlike. 

 Elongate setae (reaching at least beyond the succeeding four segments) 

 on segments 4, 8, 10, 13, and 22; the longest of these on segment 4 

 (reaching to segment 12) and on segment 22 (reaching to end of 



