AKT. 5. XOETH AMERICAN PARASITIC COPEPODS ^WILSOIs". 63 



washed with a dull rust color. The entire maxillipeds are some- 

 times crimson, in Avhich case they are not easy to distinguish against 

 the background of the gill filament. 



Total length, 5mm. Cephalothorax 1.40 mm. long, 1.S5 mm. wide. 

 Free thorax and genital segment 3.30 mm. long, the first three seg- 

 ments 1.90 mm. wide. Abdomen O.TO mm. long. Egg strings 4.50 

 mm. long. 



External specific characters of mole. — General make-up as in the 

 female, but with the bod}' narrower and more elongate. Carapace 

 one-fifth longer than wide and one-third of the length of the entire 

 body, with a very regular elliptical outline. First free segment the 

 same width as the carapace, the third and fourth segments diminish- 

 ing slightly in size, the fifth segment nearly suppressed, appearing 

 orJy as a short and narrow neck between the fourth and genital 

 segments. But small as it is it has a pair of uniramose legs, which 

 can be plainly seen in dorsal view. Genital segment relatively much 

 larger than in the female; it is fully as wide as the free segments 

 and two-thirds as long as the carapace, with strongly convex sides. 

 It is covered dorsally and ventrally with two plates which fit closely 

 to the skin. The dorsal plate is slightly emarginate at the center 

 posteriorly, and only extends to the posterior margin of the sper- 

 matophore receptacles. The ventral plate is deeply emarginate be- 

 yond the center of the spermatophore receptacles, leaving the poste- 

 rior portion of the latter uncovered. The posterior ventral portioii 

 of the segment itself is divided into two broad lobes slightly over- 

 lapping the abdomen and tipped with two spines. The sinus be- 

 tween these lobes is narrow and slitlike and extends forward nearly 

 as far as the emargination of the ventral plate. 



The spermatophore receptacles are simple, very large, almost per- 

 fectly elliptical in outline, and together fill nearly the entire seg- 

 ment. 



The spermatophores are correspondingly large, spherical, and 

 dark purple in color, and are often found attached to the genital 

 segment of the female, as in figure TO. It will be seen that they are 

 niore than half the size of the genital segment of the female and that 

 but a single spermatophore at a time could be contained in one of the 

 iQale's receptacles. They swell somewhat also on contact with the 

 sea water and are immediately surrounded with a layer of slime 

 which makes them appear still larger. Their size and their deep 

 purple color makes them conspicuous on the genital segment of the 

 female. 



The abdomen has four joints instead of three, diminishing regu- 

 larh' in width from in front backward. The two basal ones are 

 longer than the two terminal ones and have convex sides : the penul- 



