130 D. J. SCOURFIELD ON THE ENT0M0STRACA OF NORTH WALES. 



with the foregoing and also from Conway Marsh (G- S. B.), Llyn 

 Padarn, and Llyn Creigenen. As it has not previously been 

 recorded as British, it may be useful to give a few of the details by 

 which it can be distinguished from A. quadrangularis, the species 

 to which it is most nearly related. In the first place, it is a some- 

 what larger animal, measuring g^~5V* n, j wn ^ e ^-« quadrangularis 

 rarely reaches ^in. Another difference is that it possesses, in 

 addition to the coarser lines on the shell, a series of closely-set 

 longitudinal stria?, which, although very variable in intensity, are 

 always extremely fine and difficult of detection, except with high 

 magnification. The arrangement of the olfactory hairs on each 

 Antennule is a further point of distinction, for while J., affinis has 

 one of these hairs much longer than the others, and also one inserted 

 a little farther back than the rest, in A. quadrangularis all these 

 hairs are sub equal and all are inserted on the end of the Antennule. 

 Again, in A. affinis each of the two longest setaa on each branch of 

 the swimming Antenna? is provided with a little thorn at the point 

 where it is imperfectly jointed. These thorns are absent in A. 

 quadrangularis. Lastly, each of the terminal claws, with its acces- 

 sory basal tooth, is much more plainly setose in the present species 

 than in A. quadrangularis. 



Alona guttata, G. 0. Sars. This little species has only been 

 seen from Cwm Glas, Snowdon. It was there found inhabiting 

 some masses of wet alga in company with Canthocamptus pygmceus 

 and C. MacAndrewcB. 



Alona intermedia, G. 0. Sars. Only recorded from Llyn 

 Peris, where it was found in some alga taken from among clumps 

 of horse-tails. 



Alonella excisa, Fischer. I found this in several localities in 

 May last, and it also occurs in three of Prof. Brady's collections, 

 but I did not notice it in 1894. The living specimens seen by me 

 were usually much darker than 1 find them here. 



Alonella nana, Baird. (Acroperus nanus, Baird, "Nat. His*. 

 Brit. Ent.") " Tarn near the summit of Allt Wen " (G. S. B.) is 

 the only place where this has been found. 



Pleuroxus trigonellus, 0. F. Miiller. This also depends on a 

 single record, viz., one from Llyn Padarn in August, 1894. 



Feracantha truncata, 0. F. Miiller. A fairly common species. 

 Very dark- coloured examples were taken in several of the 

 lakes. 



