NO. 6.] ACCOUNT OF THE SPECIES. 105 



It is not very unlike the female, as regards the general form of the body, 

 though easily recognizable by the structure of the right anterior antenna, the 

 last pair of legs, and the tail. The latter is comparatively narrower and 

 more regularly cylindrical in form than in the female, and is divided into 5 

 well-defined segments, none of which distinguishes itself by any consider- 

 able size. 



The right anterior antenna (see figs. 3, 5) is very distinctly geniculate 

 at about the distal 3rd part of its length, and has the 4 articulations preceding 

 the geniculation rather dilated, and containing a strong muscle acting upon 

 the terminal part. Of these articulations, the last is distinguished by a very 

 conspicuous semilunar emargination of the anterior edge, defined proximally 

 by a very strong spiniform process, and distally by another process of smaller 

 size. The terminal part is considerably longer than the dilated portion, and 

 is composed of 5 articulations, the 1st of which is the largest, and somewhat 

 fusiform in shape, projecting at the end anteriorly in a small hamiform 

 prominence. 



The posterior antennae, oral parts, and natatory legs exactly agree in 

 their structure with those appendages in the female. 



The last pair of legs (PI. XXXI, fig. 12), on the other hand, are rather 

 different, and, as usual, transformed into a prehensile apparatus, subservient to 

 copulation. The 2 legs are rather unequally developed, the right being much 

 the stronger. In both legs a biarticulate basal part can be distinguished, 

 and a terminal part answering to the outer ramus, and consisting of 2 pieces, 

 movably connected with each other, the distal one more properly representing 

 2 firmly connected articulations. Not the slightest trace of an inner ramus 

 can be detected in either of the two legs. The proximal piece of the terminal 

 part in the right leg is very large, lamellarly expanded, and of an irregular oval 

 form, with 2 angular prominences outside, and containing a strong muscle, 

 acting upon the distal piece. The latter is transformed into a powerful incurved 

 claw, carrying, at some distance from the base, a small spine. On the left 

 leg, the proximal piece of the terminal part is scarcely longer than the basal 

 part, and not at all dilated, the inner edge being slightly insinuated in the 

 middle, and clothed with delicate cilia. The distal piece is of about the same 

 length as the proximal one, and terminates in a straight, denticulated spine, 



outside which a much smaller spine is attached. 



14 



