Abstract

A THIRD Calanid deserves special mention as a species of Limnocalanus, a genus known hitherto only from Scandinavian lakes. It is readily distinguished, without dissection, from the other fresh-water Calanidae, by the extraordinary length, size and prominence of the five or six terminal setx of the first maxillipeds. The second maxillipeds are also very long. The legs are all bi-ramose, the inner ramus of the fifth pair resembling the same appendage of the other legs. This species, which may be Limnoicalanus macrurns Sars, was first sent me by Mr. C. S. Fellows, of Chicago, about four years ago, a mutilated female having been obtained by him from the city water supply. The furca is as long as the entire abdomen. The rami are hairy, parallel, about seven times as long as wide, and provided with five subequal terminal sete, and one some distance in front of the external angle. It has been collected thus far only in the south end of the lake. I have found it abundant in the city harbor, even in the polluted water near the mouth of the river, where it is associated especially with Diaptomuts sicilis and the Cyclops next to be described. The Calanidae seem to have an unusual development in this country; and to facilitate their study and comparison, I have described further on all the species which I have hitherto clearly distinguished. Smallest and most abundant of the Copepoda of the lake, is a minute Cyclops (C. fluoniasi, n. s., PI. ix Figs. IO, i i and i6), only four hundredths of an inch in length (without setze) and about eleven thousandths of an inch in width, slender and colorless, with remarkably long caudal stylets; and especially noticeable for the great difference in the length of the caudal sets. The inner and outer ones are inconspicuous, while the outer of the two median setxe is longer than the furca, and the inner of these two is as long as the whole abdomen. This Cyclops was first received from Mr. B. W. Thomas, and I have since found it excessively abundant in the lake. I have not encountered it, however, in any other waters. Its nearest European ally is apparently Cyclops bicitspidatus

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