Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume VIII (1888-1891)
Birge, Edward A.
List of crustacea Cladocera from Madison, Wisconsin , pp. 379-Plate XIII ff. PDF (7.9 MB)
382 Wisconsin Academy of Sctences, Arts and Letters. NOTES ON THE PRECEDING LIST. Species 1. HOLOPEDIUM GIBBERUM, Zad. I have found this species only once in Madison. It is quite abundant in collections from northern Minnesota, and Forbes* notes its occurence at Grand Traverse Bay, Lake Michigan. Species 2. SIDA CRYSTALLINA, 0. F. Mtfller. No specimens were found belonging to the form S. elongata, DeGeer. Species 3 and 4. DAPHNELLA BRACHYURA, Li6v. and D. BRANDTIANA Fisch. Of those closely allied forms I have only to say that both are found with us, and show exactly the same differences as described and figured by Sars in his Norges Ferskvandskrebsdyr. D. brachyura is usually found in open water, and D. brandtiana in marshes. I cannot state this as a law, however, as both forms are found together sometimes, in either kind of locality. Species 5. LATONA SETIFERA, 0. F. Miller. Plate XIII. Fig. 6. Our specimens of Latona have one peculiarity not mentioned by any European writer. There is a thick coat of short hairs on the head, body and antennae. These hairs are .02 mm. or less in length, are close set and give the outline a velvety appearance when seen by transmitted light. P. E. MUller t says: " Hvad der er aldeles eiendommeligt for Latona og neppe jagttaget hos nogen anden Cladoceer, eret fint Lod af ganske korte Haar, der isaer findes over Matrix; det er vanskeligt at see og opdages kun ved staerkt Sidelys." This exact account shows that his specimens were not villous as ours are. The hairs are conspicuous in any light and are very easily seen. No other European writer mentions a similar struc- ture. A more extended study of specimens from different localities will show whether this is a local peculiarity or is characteristic of a distinct variety. On old females which have not moulted recently the hairs are worn off. The male antenna differs somewhat from the account given by Sars.$ The appendix ctliata is much larger than Sars figures it, and is situ- ated at the same level as the sense-hairs instead of distal to them. The size, number and arrangement of the seta3 on the edge of the cara- pace differ from the details given by Sars, but not in any very important respect. Latona seems to be rare in Europe, but the apparent rarity is, as Sars says, probably due to its mode of life and the method of collecting. In late summer and early fall, one can be certain of obtaining a good num- 0 Forbes, S. A. On some Entomostraca of Lake Michigan and adjacent Waters. Am. Naturalist, vol. xvi., p. 641. Aug., 1882. t Muller, P. E. Danmarks Cladocera, pp. 97-98. $ Norges Ferskvandskrebsdyr, p. 55, Pl. III, figs. 17a, 17b.
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