CRUSTACEANS 



second maxilla? converted into suckers. Scourfield records it as taken 

 in May, July and August at various stations in Epping Forest. 1 



The Cladocera, called branching horns, in allusion to their two- 

 branched second antenna;, are a very large group of very little animals. 

 They have from four to six pairs of feet, most or all of them leaf-like, 

 a character which allies them to the phyllopods, and they have the body 

 encased in a sort of bivalved covering, somewhat after the fashion of the 

 Ostracoda, only that here the head is more or less distinct. There are 

 two sets, one having the bivalved carapace well developed and almost 

 entirely covering the feet, the other with the carapace small so that the 

 feet are not covered by it. It is only with the former that we are here 

 concerned. This is subdivided into the Ctenopoda, or comb-feet, in 

 which the six pairs of foliaceous feet are all similar, branchial, non- 

 prehensile, with a comb-like arrangement of setae ; and the Anomopoda, 

 variety-feet, in which the pairs are not uniform, the front ones being 

 more or less prehensile, without branchial laminae, while the hinder 

 pairs are as in the Ctenopoda. 



In the family Sididae, of the comb-footed division, there arc two 

 Essex species, Sida crystallina (O. F. Miiller), of which Mr. Scourfield 

 says: 'This beautiful species has only been taken in the "Shoulder of 

 Mutton Pond " and the adjoining pool in Wanstead Park ' ; and 

 Diapbanosoma brandtianum^ Fischer, 1851, which has occurred more fre- 

 quently. For this latter species the synonymy is rather intricate. In 

 1850 Baird described his Daphnella ivingii from a 'pond on the edge 

 of the Colne, between Twickenham and Whitton, Middlesex." The 

 generic name had to be given up. It was preoccupied. The specific 

 name was also given up, on the ground that Baird's species had been 

 already named Sida brachyura by Lievin in 1848, with which some 

 authors further identify Fischer's brandtianum. Others uphold this as 

 distinct, and Mr. Scourfield affirms that the Epping Forest forms 

 evidently belong to it. At the same time he places in the synonymy 

 ' Daphnella ivingii (in part), Baird.' This however is inconsistent, for if 

 Fischer's species be distinct from Lievin's but identical with Baird's, the 

 earlier name must stand, and the species will be Diapbanosoma wingii 

 (Baird). 



The Anomopoda are divided into four families, over which the 

 majority of the Cladocera are distributed. Of these families the most 

 familiar is that of the Daphniidae, and in this the typical genus Daphnia, 

 after frequent restrictions, still retains numerous species. From Epping 

 Forest Mr. Scourfield reports Daphnia magna, Straus, D. fu/ex, de Geer, 

 D. ottusa, Kurz, D. /acustris, Sars, D. longispina, O. F. Miiller, D. hyalina, 

 Leydig, >.(?) ga/eata, Sars, and D.(?) cucullata, Sars. It would be pleasing 



1 It may be sufficient to refer here once for all to Mr. Scourfield's Papers on ' The Entomostraca 

 of Epping Forest, with some General Remarks on the Group,' in The Essex NaturaRit, vol. x. pp. 193- 

 tio (1897); vol. x. pp. 159-74 (1898); vol. x. pp. 313-34 (1898), the last part containing a 

 valuable bibliography of the subject, in addition to a detailed list of the Epping Forest species, to which 

 my quotations refer when not otherwise noted. 



1 British Entomtstraea, Ray Soc. p. 1 1 o. 



211 



