D. J. SCOURFIELD ON THE ENTOMOSTRACA OF NORTH WALES. 131 



Chydorus sphericus, O. F. Miiller. In North Wales, as in 

 most other parts of the British Isles, this is probably the 

 commonest of all the forms of Cladocera. 



Chydorus caelatus, Schoedler. Seen only in two localities, viz,, 

 Llyn Padarn and Llyn Dvvythwch. 



This species was first recorded as British by Prof. G. S. Brady, 

 in 1868, in the "Intellectual Observer," Vol. xii., p. 423, under 

 the name of Lynceus sphericus, var. favosa. It does not appear to 

 have been subsequently noted, and has most probably been 

 mistaken for the common C. sphericus. It is easily distinguished 

 from the latter, however, by its shell sculpture, which consists of 

 rows of deep pits (most plainly developed on the ventral and 

 posterior portions of the valves) unaccompanied by any evident 

 reticulation. The valves of typical C. sphericus, on the other 

 hand, are never pitted, but always reticulated. In other respects 

 the present form is extremely close to C. sphericus. 



Chydorus latus, G. 0. Sars. This is the same as recorded by 

 me in 1892 as C. ovalis, Kurz. (" J. Q. M. C," Ser. II., Vol. v., p. 

 68). I now think that this form agrees better with C. latus 

 than C. ovalis, and I have, therefore, adopted the former name. 

 The two species, however, seem to be very closely allied, and have 

 even been considered identical, as by Hellich, for example. The 

 records for this species have been Llyn y Own, Llyn Teyrn, and 

 Bog near Llyn Peris. All the specimens seen were rather 

 smaller than those recorded from Leytonstone in the above- 

 mentioned paper. 



Polyphemus pediculus, De Geer. During August, 1894, this 

 species occurred pretty frequently in the Snowdon district, but I 

 saw very few specimens in May last. 



Bythotrephes longimanus, Leydig (B. Cederstromii, Beck — 

 " Some New Cladocera," &c.) Recorded only from Llyn Padarn and 

 Llyn Peris. It no doubt lives in many of the larger and deeper 

 lakes, but owing to its exclusively pelagic habits it is not easily 

 captured without the aid of a boat. 



Leptodora hyalina, Lilljeborg. Like the foregoing, this species 

 is difficult to capture from the shore, but I managed to get it in 

 this way in Llyn Llydaw. The other localities where it has been 

 noted are Llyn Padarn, Llyn Peris, and Bala Lake. 



