64 l>. J. SCOURFIELD ON BRITISH CLADOCERA. 



similar to those of the common Simocephalus vetulus. The 

 strise occasionally coalesce, thus enclosing long lenticular areas. 

 On the ventral margin they merge into an irregularly hexagonal 

 reticulation. Tail obliquely truncate at its extremity, and pro- 

 vided with a double series of spines on each side of the anus. 

 Anterior to the latter is also a median line of little curved 

 thorns, diminishing in size forwards. The outer or principal of 

 the two anal rows consists of from seven to nine spines, the 

 longer or posterior ones being nearly straight and sharp as 

 needles. The inner row comprises a larger number of smaller 

 spines, but it can only be seen with some difficulty between the 

 large spines of the outer row. The two terminal tail claws are 

 rather slender, with a lateral line of fine hairs, but are without 

 accessory teeth. There are two dorsal spurs on the abdomen, 

 the posterior being only about a quarter of the length of the 

 anterior. The number of eggs carried at one time in the brood 

 chamber is often numerous, sometimes as many as ten. Ephip- 

 pium with one egg. Length ^'g^in. 



The following are the places where I have so far found it : — 

 Wanstead Park, Essex, August and September, 1889, May to 

 October, 1890, August and September, 1891 ; Ditch at Horning 

 Ferry, Norfolk, August, 1890 ; Golding's Hill Ponds, Loughton, 

 Essex, August, 1891. 



Male. — My specimens were reddish all over, and could be 

 easily distinguished from the female by their colour, even with 

 the naked eye. The head is more erect than in the female, and 

 more deeply bayed on the top. Dorsal margin of the shell very 

 nearly straight, with the blunt angle minutely spined. The 

 shell markings are peculiar. At the ventral margin they consist 

 of irregular hexagons as in the female, but across the middle of 

 the valves they are somewhat diamond-shaped, intermediate, in 

 fact, between true hexagons and the long striee characteristic of 

 the female. The tail is almost identical in shape and armature 

 with that of the female. The antennules and first pair of feet 

 are, however, very different. The former are much elongated, 

 and apparently two-jointed. The lateral seta is near the middle 

 of the long joint, which also bears at its tip the usual bunch of 

 sensory hairs and a long flagellum. This flagellum, which is 

 about the same length as the antennule, is slightly bent towards 

 the body in the middle of its length, and terminates in a small 



