170 D. .1. SCOURFIELL) ON ENlOMOS'l'llACA. 



Baird, Nat. Hist. Brit. Ent., Tab. vii, Fig. 5 ; Scourfield, 

 J.Q.M.C, Ser. ii, Vol. v., p. 63, PI. IV., Figs. 1-3). 



Ceriodaphnia rotunda, Straus {Daphnia rotunda, Baird, Nat. 

 Hist. Brit. Ent., p. 98, Tab. ix.. Fig. 6, and Tab. x., Fig. 4). 



Ceriodaphnia reticulata, Jurine (Daphnia reticulata, Baird, 

 Nat. Hist. Brit. Ent., p. 97, Tab. xii.. Figs. 1-2). Two modifi- 

 cations of this species occur at Wanstead Park. The most 

 evident distinction between them is to be found in the shape of 

 the fornices covering the bases of the large antennae. In one 

 case these are quite round, but in the other they are produced 

 into strong cusps. Males of both forms have been observed. 

 This species is the least common of the genus. 



Ceriodaphnia quadrangula, O. F. Miiller (Scourfield, J.Q.M.C, 

 Ser. ii., Vol. v., p. 65, PI. IV., Figs. 4-7). 



Scapholeheris mucronata, 0. F. Miiller {Daphnia rtiucronata, 

 Baird, Nat. Hist. Brit. Ent., p. 99, Tab. x.. Figs. 2-3). The 

 two well-known varieties of this species both occur at Wanstead 

 Park, but the "acute rostrata" or "cornuta" form is much 

 more common, and has a longer period of activity than the 

 " obtuse rostrata " form. From its rarity and late appearance, 

 I suspect that the latter is simply an advanced stage of the 

 former, i.e., a single individual, if living long enough, would 

 pass successively through the " acute " and "obtuse rostrata" 

 forms. The male of this species, recorded 3rd October, 1891, 

 was without the cephalic cornu, although all the females taken 

 at the same time, both with and without ephippia, were of the 

 " acute rostrata " type. 



Simocephalus vetulus, 0. F. Miiller (Daphnia vetula, Baird, 

 Nat. Hist. Brit. Ent., p. 95, Tab. x., Fig. 1). This is the 

 commonest and hardiest of the Cladocera of Wanstead Park. 

 It has been taken repeatedly in all the ponds, and figures 

 through the whole of the record without a single break. 

 Directly after the frost of 1890-91, it was the only representa- 

 tive of its order that could be found. On one or two occasions 

 [ have seen specimens that would, probably, be better referred 

 to S. exspinosus, De Geer, if that can be considered a sufiiciently 

 well-marked form to merit a distinct name. 



Daphnia pulex, De Geer (Baird, Nat. Hist. Brit. Ent., p. 89, 

 Tab. vi., Figs. 1-3, etc.). It is impossible to say for certain 

 whether the Wanstead Park forms referred to D. pulex are 



