Page:VCH Surrey 1.djvu/235

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CRUSTACEANS company of specimens from the dried mud examined last year included three species of Cladocera and two of Ostracoda. Of those which have reappeared this spring, one of the Ostracoda species is now in the ascendant. Of the Cladocera, or branching-horned Entomostraca, so-called from their two-branched second antenna?, there are in Surrey several species well adapted to gratify the microscopist, and to direct the attention of collectors and students in general to the divisions and subdivisions of this important group. There are two principal sections. In the first, which is also the more extensive, the feet are pretty well covered by a bivalved carapace. This section contains two tribes, the Cten6poda, called ' comb-footed,' from the comb-like arrangement of setas on their six pairs of similar feet, and the Anom6poda, in which, as the name implies, the feet are not all similar. The former tribe contains two families, one of which, the Sididae, is here represented by Sida crystallina (O. F. Miiller), recorded by Baird from a 'ditch near Richmond, oppo- site Isleworth,' 1 and by members of the Quekett Microscopical Club from Walton, Woking and Richmond Park. 2 In the same family, and also taken by Baird from a ' ditch near Richmond, opposite Isleworth,' 3 stands Daphnella wingii, which has large eyes and very large antennae, but a tail that is by comparison tiny. The proper generic name is Diaphanosoma, in agreement with the ' beautiful, clear, crystalline trans- parency ' of its carapace, and perhaps it should be called D. brachyurum (Lievin), the short-tailed Diaphanosoma, but about this there is some uncertainty, so that with an alternative perhaps it may have to be distinguished as D. wingti. The tribe of the Anomopoda contains four families. The first of these is the Daphniidas, a powerful clan, in numbers numberless, so predominant as a rule in the horse-pond that it can scarcely fail to make the horse willy-nilly a carnivorous animal. Among the speci- mens reared from the dried mud above mentioned those assignable to Dapbnia were however not very numerous. They were small, with the surface reticulation during life very conspicuous, the terminal spine of moderate length, and the abdomen dorsally not strongly sculptured. The species appear to be Dapbnia longispina (O. F. Miiller). Possibly in youthful stages many of their kindred fell victims to the better pro- tected Ostracoda. Apart from this private hatchery there are records showing that more than one species of Dapbnia or its nearest kindred are to be found in Surrey. Thus in a paper on ' Pond Life ' Mr. W. Low Sarjeant, speaking of Mitcham Common, says: 'Just after passing the windmill there is a large duck-pond, which in the autumn especially swarms with a giant race of Dapbnia, many of them exceeding an eighth of an inch in length, and I have taken them three-sixteenths of an inch 1 British Entomostraca, Ray Soc. p. 109 (1850). 3 Journal of the Q. M. C. ser. 2, vol. ii. p. 191 (1884) ; vol. iv. pp. 171, *73, 326 (1888, 1889). 3 British Entomostraca, p. 1 1 o. I 193