1885.] 



CLADOCEEA. 



39 



The Ist pair of legs (lig. 2) are comparatively power ful in 

 structure, and strongly curved, forming anteriorly a geniculate 

 bend, whence a faint line may be traced crossing the trunk, and, 

 as it were, dividing it into two segments. Along the anterior 

 border, occur several biiDches of delicate curved bristles, and a 

 little within the margin 2 strong, anteriorly curving spines are 

 found to project from the base of the distal segment. At the 

 apex, the leg divides into 2 irregular branches, the inner of 

 which (endopod) constitutes a rather broad and semi-membranous 

 plate, fringed with 9 strong plumous setæ, arranged in 3 sets. 

 The outer branch (exopod) is more slender, and exhibits 2 unequal 

 lobes, the posterior being much the larger and conically produced, 

 as also bearing at the tip an exceedingly long bi-articulate 

 seta, somewhat bent anteriorly and denticulate along the front 

 edge. The anterior lobe is comparatively small, but provided 

 with 3 setæ, 2 of which exhibit a similar aspect to that of 

 the inner lobe, though much smaller in size, whereas the 3rd 

 seta is quite smooth and curved anteriorly in a hook-like manner. 

 All of the setæ on the exopod project, as a rule, beyond the valves 

 of the carapace anteriorly (see Pl. 7, fig. 1), and would seem to 

 be prehensile in character. Moreover, on the exterior face of 

 the proximal segment of the leg, is affixed a small rounded 

 vesicular corpuscle, representing apparently the epipod, and mor- 

 phologically corresponding to the gill in other Crustacea. Of 

 the so-called maxillary process — so distinctly developed on the 

 succeeding pairs of legs — I have failed to detect any trace 

 whatever. 



The 2nd pair of legs (fig. 3) are much shorter, and have the 

 distal segment of the trunk very broad and appressed, as also 

 exhibiting on the edge 7 strong bi-articulate and, as it were, 

 digitiform spines, diminishing successively in size inwards, all of 

 them with the outer joint densely ciliate along one of the edges. 

 At the exterior corner of this segment, — properly representing 

 the endopod, — is affixed a simple conical lobe (apparently the 

 exopod) bearing at the tip an exceedingly strong and curved 

 seta, of a similar appearance to that originating from the exopod 



