172 Mr. W. West and Dr. G. S. West. [Oct. 30, 



Of a total of 246 species observed in the phytoplankton, 417 per cent, 

 were Desmidiacea?, 19 per cent. Bacillarieae, and 13-3 per cent. Myxophyceae. 



Fig. 2. — -Peridinimn limbatum (Stokes), Lenim., from the Plankton of a small Lake between 

 Clifden and Eoundstone, Galway. x 500. The reticulated surface markings of the 

 cell-wall are only indicated on one of the plates. 



V. Lough Neagh. 



The first contribution to the plankton of the Irish lakes was an account of 

 the plankton- Alga? of Lough Neagh and Lough Beg * the material having 

 been collected in May, 1900, and July, 1901. This material has since been 

 subjected to a further examination. The lake is so isolated, and, moreover, 

 so differently situated from the other Irish lakes examined, that we have 

 kept the records in a separate column in the tabulated list of British phyto- 

 plankton. It is also of interest as being the largest lake in the British 

 Islands ; but although covering a large area it is very shallow, its average 

 depth being only 45 feet, and the deepest sounding (made in the north-west 

 corner), is only 96 feet. 



The phytoplankton consists largely of Diatoms, Peridinieee, and Chloro- 

 phycese. Of the latter, a few of the Desmids characteristic of shallow lakes 

 are abundant, and Staurastrum paradoxum, var. longipes, occurs in prodigious 

 quantity. St. pelagicum was first described from this lake, and has since been 

 found in the lakes of Germany and Iceland. The Protococcoidese are very 

 well represented, species of Coslastrum, Pediastrum, and Oocystis being 

 especially noticeable. Of the Diatoms, Tabellaria fenestrata, var. asterionel- 

 loides, is the most conspicuous, but Goscinodiscus lacustris, Cymatopleura 

 elliptica, and species of Surirella are also abundant. The Myxophyceae are 



* W. and G. S. West, "A Contrib. to the Fresh w. Alg. of the North of Ireland," 'Koy. 

 Irish Acad. Trans.,' vol. 32, sect. B, part 1, 1902. 



