14 A EEVISION OF THE BRITISH SPECIES OF 



the longer of the two, being equal in length to the whole abdo- 

 men ; of the lateral setae the outer is the longer ; the inner one 

 is so closely appressed to the long seta as to be almost invisible ; 

 the outer margins of the rami bear near the extremity a single 

 short seta. The anterior antennas are rather stout, only slightly 

 tapered towards tho apex, and do not exceed in length the first 

 body-segment. The posterior border of the posterior maxilliped 

 is irregular, having near the base a slight abrupt prominence, 

 each end of which forms an obscure tooth : this structure is 

 variable in development but is usually more or less distinctly 

 visible. Both branches of all the swimming feet are three- 

 jointed, and the terminal joint of the outer branch bears on its 

 outer margin two spines, on the inner margin three long setae, 

 and at the apex a single spine and a seta ; but in the case of 

 the first pair of feet, the last joint of the outer branch has two 

 lateral spines only, the usual apical spine being absent. The 

 feet of the fifth pair are extremely small (-027 mm., exclu- 

 sive of setae), two-jointed, the first bearing only one long apical 

 seta, the second one long seta and a much shorter, stout spine. 

 Length 1*3 mm. Colour (of spirit specimens) very deep, opaque 

 brown (Windermere); bluish, semi-opaque (Wanstead Park). 



I have specimens of this species which were taken several 

 years ago in Windermere amongst weeds at the surface of the 

 lake, and one (probably this species) from a deep-net gathering 

 taken in Ellesmere Lake, Shropshire. It occurs also in gather- 

 ings from Lambton Park, county Durham [Rev. Dr. Norman) ; 

 and from Duddingston Loch, near Edinburgh [Mr. T. Scott). 

 I am indebted to Mr. D. J. Scourfield for others taken 

 in 1890 and 1891 at W^anstead Park, Essex: more recently 

 Mr. Scourfield has sent me the following supplementary list 

 of stations : — Hackney Marsh ; Leytonstone ; Royal Botanic 

 Gardens, Regent's Park ; Cuckoo Pits, Chingford ; Southend, 

 Essex ; Higham Park and W r arner's Pond, Woodford ; Pavenham, 

 Bedfordshire. 



The specimens generally agree very exactly with the descrip- 

 tion of Professor Gr. 0. Sars, except as to the spines of the 

 fourth pair of feet. Respecting these Sars says, " aculeorum 



79 



