CRUSTACEANS 



observers, Dr. G. S. Brady, Dr. David Robertson, and the Rev. Dr. 

 Norman. In a joint paper the first two say : ' The Entomostraca of 

 the tidal waters of Norfolk, Suffolk, and the Cambridge fen district 

 constitute so remarkable a group that it seems best to speak ot them 

 separately ; and in so doing we shall call the area to which we refer 

 the East-Anglian district, understanding by that term the whole tract 

 drained by the rivers Nene, Cam, Bure, Yare, and Waveney.'^ They 

 think it possible that the fen district of Lincolnshire may also have been 

 continuous with the other tract in former times. They discuss the 

 changes which the physical features of East Norfolk have undergone, 

 making a sea-covered bank the site of a large town, and leaving lakes 

 and tortuous streams where was once a marine expanse. They give evi- 

 dence that the process of silting up is still at work. Finally, they draw 

 the following conclusions : ' There can be no difficulty, then, in under- 

 standing how a fauna, introduced when the whole East-Anglian district 

 was overspread by the sea, should hold its ground for a lengthened 

 period, while its habitat was year by year becoming less subject to 

 marine influences, and that the more hardy or more plastic species 

 should remain even after fresh water entirely usurped the place of salt, 

 while at the same time a new fauna derived from the landward side was 

 also gradually establishing itself, as the conditions of existence became 

 more favourable.'^ From numerous surface gatherings the two authors 

 obtained a considerable collection of Entomostraca belonging to various 

 groups, but these were swimming species of purely freshwater character, 

 such as might have been found, they explain, in any British waters of 

 like extent. In their dredged material, on the other hand, they found 

 several new and peculiar Ostracoda. As these little bivalved crustaceans 

 in outward appearance are just like bivalved molluscs, when only empty 

 valves are found, confusion easily arises. Accordingly, what was de- 

 scribed by Brady and Robertson in 1870 among the Ostracoda of the 

 Norfolk Ouse as Goniocypris mitra nov. gen. et sp., is explained by Brady 

 and Norman in 1889 to be the fry of the mollusc Anodonta cygncea? 

 Another form, Polycheles stevensoni, which they found in the Ouse and 

 many other localities, was a genuinely new discovery, both as to genus 

 and species ; but the generic name was twice changed, first into Dar- 

 winella and then into Darwinula, both Polycheles and Darwinella being 

 pre-occupied. The species now stands by itself in the Darwinulids, 

 third family of the section Podocopa. Argillcecia aurea, Brady and 

 Robertson, is made a synonym of it by Brady and Norman in 1889.^ 

 In the Cytherid^, the fourth family of the same section, stands Meta- 

 cypris cordata, another new genus and species, discovered by Brady and 

 Robertson in Wroxham and Barton broads, and at other East-Anglian 



^ Annals and Magazine of Natural History, ser. 4, vol. vi. p. 3, 1 870. * Ibid. p. 4. 



' Monograph of the Marine and Freshwater Ostracoda of the North Atlantic and of North- 

 Western Europe, section I., ' Podocopa,' by George Stewardson Brady, M.D., F.R.S., F.L.S., 

 and the Rev. Alfred M. Norman, M.A., D.C.L., F.L.S. ; Trans. Royal Dublin Soc, ser. 2, 

 vol. iv. p. 120. 



* Ibid. p. 122. 



I 193 



