Rupert Jones, on Bhalved Entomosiraca. 47 



presence of this or that kind of Entomostraca ; and in some 

 instances thin intercahxted bands of freshwater or of estuarine 

 deposits, amongst marine strata, can be indicated by the pre- 

 sence of Estherice, which in past, as in present, times appear 

 to have avoided sea-water, though Hving abundantly in salt- 

 marshes and lagoons. See the ' Monograph of Fossil Esthe- 

 rice,' 1862. 



Thus, also, Mr. G. S. Brady observes {' Intellectual Ob- 

 server,' 1867, p. Ill), in noticing the geological interest of 

 Entomostraca, " My belief is, therefore, that those strata 

 which exhibit such very abundant and closely packed re- 

 mains of the smaller CypridaB and Cijtherida have most likely 

 been formed in shallow, brackish lagoons, or at the mouths 

 and deltas of rivers. The species of Ostracoda which I have 

 found in these situations are Cytheridea torosa (Jones), Cy there 

 pellucida, Baird, and Loxoconcha elliptica, Brady ; while in 

 water a little further from the saline influence, but still 

 slightly partaking of it, it is not uncommon to meet Avith 

 Cypris salina, Brady^ and Cypridopsis aculeata, Lilljeborg, 

 as well as Entomostraca belonging to other orders." 



The Entomostraca act pre-eminently as scavengers in both 

 salt and fresh waters. Most of the groups (as Copepods, 

 Ostracods, and Phyllopods) comprise both marine and fresh- 

 water species ; but the Cladocera are confined to fresh 

 water. The excessive swarming of the pink Daphnia or 

 Water-flea has occasionally reddened pond-water so strongly 

 as to have seemed supernatural to our ancestors, and to have 

 produced terror, as an evil omen, among the ignorant. 

 Amongst the British Ostracoda, Cypris, Cyprodopsis, Noto- 

 dromas, and Candona, are inhabitants of lakes, ponds, ditches, 

 streams, and rivers ; and they can be readily obtained and 

 conveniently kept and studied in the aquarium. Paracypris, 

 Pontocypjris, Bairdia, and Macrocypris, are marine members 

 of Mr. Brady's group " Cypridae." Excepting the fresh- 

 water Limnocy there, all the Cytheridce are marine, Cythe- 

 ridea and Loxoconcha having also a taste for brackish water. 

 These salt-water species of the Bivalved Entomostraca are 

 distributed in deep and shallow seas, in pools on the beach 

 between tides, in lagoons and back-Avaters, and in the brack- 

 ish water of estuaries and salt-marshes. The ' Trans. Zoolog. 

 Soc.,' 1867, contains a memoir, by Mr. G. S. Brady, descrip- 

 tive of some new forms of Ostracoda, in which we find some 

 " habitats " referred to as being in " shallow water," and 

 others. at 14, 17, 30, 43, 60-70, 223, S60, 470, and even 

 2050 fathoms. 



The Cyprida, having plumose '^ antennae," or natatory 



