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Show 1892.] AQUATIC OLIGOCH^TOUS WORMS. 355 contractile. This species is, of course, freshwater in habitat. It was found in a forest-pool along with Phreoryctes smithii. None of the specimens were mature, so I a m unable to say how far they may agree with Clitellio in other particulars; but, in any case, they have the two pairs of dilated vessels in viii. and ix. that have hitherto served to distinguish Clitellio from Limnodrilus. v. On a new Genus (Kerria) intermediate between Acanthodrilus and Ocnerodrilus. Mr. J. Graham Kerr, who accompanied the " Pilcomayo Expedition " in 1890, has kindly given m e a number of small Oligochaeta which he collected in the upper reaches of that river. They were preserved with corrosive sublimate, and are in consequence in an excellent condition for microscopical examination. There are altogether about a dozen specimens, some fortunately being sexually mature. The water where they were met with was exceedingly salt and bitter, but contained a number of other animals, notably a few decapod Crustaceans. But animal life was not, M r . Kerr informs me, very abundant in the stream. So far as I a m aware, no Oligo-chaete of any kind has ever been described from a locality like the present, except a species of Pachydrilus referred to by Semper as occurring in the brine-springs of Kissingen in Germany. Salt water is not, however, entirely inimical to the existence of Oligochaeta, for there are a few species known from the sea-shore; for example, Clitellio, referred to in the present paper, Pontoscolex, Pontodrilus, &c. I expected, therefore, that these worms would prove to be interesting, and m y expectations were realized. The worms are all very small, an inch to an inch and a half in length by 1 m m . in diameter. They are about the size of, and resemble in general appearance, Ocnerodrilus eiseni, and I at first was disposed to refer them to the same genus at least. Although a more careful examination of the worms showed that they could not be referred to the genus Ocnerodrilus, it became very soon evident that they were nearly related to that genus; they serve, in fact, to indicate the probable relations of Ocnerodrilus, concerning which I was formerly in doubtl. Eisen, the original describer2 of the genus Ocnerodrilus, placed it in the family Lumbriculidae. This conclusion was subsequently abandoned by Eisen himself3, and I have myself1 endeavoured to combat it; the genus is clearly to be referred to that very large and imperfectly known group of worms which I have called Cryptodrilidas. I do not propose to give a detailed systematic account of the anatomy of this new worm, but merely to dwell 1 " On the Anatomy of Ocnerodrilus (Eisen)," Tr. Roy. Soc. Edin. vol. xxxvi. No. 21. 2 " On the Anatomy of Ocnerodrilus," Nov. Act. Reg. Soc. TJpsal. ser. 3, vol. X. 3 "On the Anatomy of Sutroa rostrata, &c," Mem. Calif. Ac. Sci. vol. ii. no. 1. 4 Loc. cit. p. 580. |