Freshwater Entomostraca of South America. 239 



tinned into the next segment, which also has three muscles, 

 firstly, a flexor which, rising at the base of this segment, is in- 

 serted into the inner side of the apex of the penultimate segment 

 of the inner branch. The other two are the flexor and extensor of 

 the larger branch, and are inserted into its base. This larger 

 branch also contains a muscle similar to that of the smaller one. 

 The specimens, however, have been so long preserved in spirits 

 that it is difficult to make the muscles out with certainty, and in 

 some specimens the arrangement appeared to be difl^erent. 



The fifth pair of legs in the female are gJg- inch in length, and 

 similar to one another. They are formed on the same plan as 

 the other legs, from which they differ in several particulars, but 

 chiefly in the shortness of hairs. The basal portion, as usual, con- 

 sists of two segments, the second of which is slightly bifid at the 

 apex, and bears a sm;ill hair. The larger branch is composed of 

 three segments, of which the basal bears a large spine at the out- 

 side of the apex ; the second, a large spine on each side of the 

 apex, the inner one of which is provided with a row of little 

 spines on its upper edge, and the apical three spines ; the lesser 

 branch, which is also 3-jointed, has the two basal segments each 

 provided with a spine on the inner side of the apex, and the ter- 

 minal segment armed with six spines. 



Those of the male are larger, about J^ inch in length, and non- 

 symmetrical. The right is rather the largest. The basal portion, 

 as usual, consists of two segments, and bears two branches, the 

 inner one small and 3-jointed, the apical segment armed with four 

 spines. The outer large branch also consists of three segments, 

 the two basal ones each bearing a spine at the apex externally. 

 The second segment of this branch is crossed by a line, which 

 appears to indicate that it consists nominally of two segments, 

 especially as I have observed the same appearance in other species. 

 The terminal joint has the form of a very large spine, and tapers 

 very much to the end, which seems drawn out into a filament, and 

 turned back. The apical half is dotted with a row of very fine 

 teeth. 



The left leg is rather smaller ; the inner branch and the spine 

 on the basal segment of the outer branch are wanting. The ter- 

 minal segment is similar in form to that of the other legs, from 

 which, however, it differs in having a spine externally at about a 

 quarter of its length from the base, in not tapering quite so much, 

 and in wanting the row of teeth or bristles. 



The abdomen of the female consists of three segments, the first 



