Phreatoicus kirkii, sp. nov.
Specific Diagnosis.—General appearance of the body and appendages very similar to that of P. assimilis. Eyes not visible. Body rather stout and compact, the segments of the pereion fitting closely to one another; pleura of the 2nd to 5th segments of the pleon largely developed, fully as deep as their segments and concealing the pleopoda, rounded below and with the inferior margin and the lower part of the hind margin thickly fringed with long setæ; 5th segment as long as the 3rd and 4th together; inferior margin of the 6th segment with six curved seté which increase in stoutness posteriorly, the last being very stout; the projection at the end of the last segment narrower (as seen in side view) than in P. assimilis, longer than broad, tipped with two or three stout setæ and bearing also several more slender ones; below this the hind margin on each side is irregularly convex, and bears numerous short setæ of varying degrees of stoutness. Surface of body with a fair number of slender setæ arranged singly or in small tufts, and becoming more numerous posteriorly, especially on the last segment of the pleon. Lower antennæ scarcely half as long as the body; flagellum of about twelve joints, not much longer than the peduncle. Pereiopoda as in P. assimilis, rather short and very spiny; the 1st forming in the male a powerful subchelate claw of the same general structure as in P. assimilis, but with the anterior produced portion of the meros armed with one stout seta and a few slender ones in place of the thick brush of fine hairs found in P. assimilis; 4th pereiopod of male shorter than the 3rd and specially modified. In the female the 1st pereiopod has the subchelate claw much smaller and like that described for P. typicus, and the 4th pereiopod is similar to the 3rd. The last three pairs of pereiopoda with the basa considerably expanded. The mouth parts are practically the same as in P. assimilis, the lower lip having the lobes rounded, and the inner lobe of the first maxilla bearing only four plumose setæ.
Length—cephalon, 2·5 mm.; pereion, 8·5 mm.; pleon, 6·5 mm. Depth—pereion, 2 mm.; pleon, 3·5 mm.
Hab.—Fresh-water lagoon on Ruapuke Island.
The description given above applies to the Ruapuke Island specimens. Those from the neighbourhood of Dunedin differ considerably in general appearance, having the segments of the pereion longer, so that the appendages are more separated, and there are also some minor differences. I was at first inclined to consider them as a separate species, but the resemblances in the appendages are so close, and the differences rather in the proportions of the body—characters difficult to estimate precisely, and perhaps partly due to shrinkage caused by the preserving-fluids used—so that I propose to consider them as a variety.