36 PROCEEDINGS OF THE ACADEMY OF [Jan., 



First pair — outer ramus, four spines, four setae; inner ramus, one 



seta, one spine, four setse. 

 Second pair — outer ramus, four spines, five setse; inner ramus, one 



seta, one spine, four setse. 



Third pair — like second. 



Fourth pair — outer ramus, three spines, five setse; inner ramus, one 

 seta, two spines (inner smooth-edged), two setse (distal one 

 reduced) (see PI. I, fig. 14). 



The lower row of spinules on the lamella connecting the basal 

 segments of the third pair of swimming feet is very large and well 

 •developed (about twelve coarse spinules). 



The fifth foot (PI. I, fig. 13) is essentially like that of C. fuscus 

 Jurine. Lilljeborg, in his PI. Ill, fig. 21, shows the fifth foot differing 

 from that of C. fuscus (fig. 13) on the same plate by the absence of 

 the rows of spinules on the two segments. The fifth foot consists 

 of two segments. The basal segment is slightly convex on its outer 

 margin, while the inner margin is correspondingly concave (see 

 PI. I, fig. 13). Toward the inner lateral surface of this same segment 

 there are several, usually three, rows of well-developed spinules. 

 At the outer distal corner it bears a long seta, plumose on its distal 

 half. The distal segment is set well towards the inner side of the 

 lower segment and at the point of juncture is ornamented with a 

 f circle of small spines. It bears on its tip two heavy spines and a 

 slender seta. The inner spine is slightly longer than the outer. 

 At its base there is a semicircle of quite prominent spinules. Both 

 of these spines are more densely plumose on their inner edges. Be- 

 tween them and borne at the end of a truncated cone-shaped projec- 

 tion is the long middle seta. It is only slightly plumose at its distal 

 end, and these hairs (8-10 on each side) are placed at regularly 

 diminishing intervals. 



The shape of the receptaculum seminis (PI. I, fig. 12) can be readily 

 noted. The anterior division is almost elliptical when fully dis- 

 tended. The posterior portion is two-lobed and has the form of a 

 low, widely spread letter w. This organ is practically colorless, and 

 for this reason its form can be unmistakably observed. 



The egg-sacs (PI. I, fig. 2), carried at a considerable angle from the 

 abdomen, are nearly as long as the abdomen. In a 9 in which the 

 abdomen measured .6 mm. the egg-sacs were .57 mm. long. 



In discussing the size of this species, Forbes states that "the 

 usual length of the female in America is from 1.26-1.4 mm., but it 

 seems to be much greater (2.5 mm.) in the European representatives 



