CRUSTACEANS 



and C. scitu/a, Herrick. The first four are noted by Baird under the 

 genus Daphnia, but he regards quadrangula as only a variety of reticu/ata. 

 Herrick's species, being new to the British fauna, is described and 

 figured by Mr. Scourfield. After noting its rather large size and the 

 comparatively small hexagons in the reticulation of its valves, he con- 

 tinues : * The fornices 1 are prominent, but not angulated, though in the 

 males there may be an indication of a tooth at the point of greatest 

 extension. The antennules in the female are small, but those of the 

 male are large, being, in fact, probably larger than in any other known 

 species, with the exception of C. megalops. The post-abdomen is 

 tapered towards the end, and is furnished with about ten anal teeth. 

 The terminal claws are without combs. The females carry about eight 

 eggs in the brood chamber, and these are retained in position by a 

 very large spur, which quite overshadows the little projection occupying 

 the place of the second spur.' 



In Scapholeberis the ventral margin of the valves is almost straight, 

 with no convergence between it and the dorsal margin as in Dapbnia. 

 In Simocephalus the reticulation of the valves is formed by long transverse 

 lines instead of small meshes. Both these genera were separated from 

 Daphnia by Schodler. They yield to Essex Scapboleberis mucronata 

 (O. F. M tiller), with its variety cornuta, and the very common Simo- 

 cephalus vetu/us (O. F. Miiller), together with 5. exspinosus (de Geer), 

 a species so near to its neighbour that Mr. Scourfield apologizes for the 

 smallness of the distinctions between them. Of the Scapholeberis , he 

 says : * The evidence from the whole of Epping Forest is the same as 

 that already recorded from Wanstead Park, namely, that during the 

 earlier part of the annual period of activity only the cornuta form is 

 to be found, the typical form not making its appearance until August at 

 the earliest.' Of Moina rectirostris (O. F. Miiller), from the margin of 

 the Warren Pond, Chingford, he notes that the ephippium contained 

 only one egg. Generally in the Daphniidae this ' saddle ' contains two 

 eggs. The eggs laid in this strange casket are called ' resting-eggs ' or 

 winter eggs, and will not hatch without fertilization. When this has 

 occurred, at the next change of the mother's skin, the ephippium or 

 case formed for sheltering them is thrown off along with it, and they 

 can rest in patient security till a favourable season for their development 

 comes round. The ordinary eggs develop parthenogenetically within 

 the matrix, and without need of a father. 



From the small family Bosminidae Essex is credited with Bosmina 

 longirostris (O. F. Miiller) and its near ally B. cornuta (Jurine). 



For the next family Mr. Scourfield adopts the name Lyncodaphnidae, 

 but this from its earliest genus should rather be called Macrotrichidas. 

 It is illustrated in this county by Ilyocryptus sordidus (Lievin), a non- 

 swimming species, with an unflattering name that means 'the mud-hidden 

 dirty one,' and by two species of the typical genus, Macrothrix laticornis 



1 Thee so-called arches are chitinous projections at the sides of the head, uniting it with the 

 thorax. 



213 



