ALGOLOGICAL NOTES 83 



Chlorophyce^. — Netrium Digitus (Ehrenb.) Itzig. & Eothe, 

 Penium Navicula Br6b., Tetmemorus granulatus (Breb.) Ealfs, 

 Euastrum oblong iiin (Grev.) Ealfs. 



Bacillarie^. — Eunotia Arciis Ehrenb., E. hinaris (Ehrenb.) 

 Grun., E. pectinalis (Kutz.) Eabenh., Achnanthes linearis W. Sm., 

 Navicula a232Jendiculata Kiitz., N. atomoides Grun., N. horealis 

 Ehrenb.', N. Brehissonii Kiitz. var. diminuta V. Heurck, N. con- 

 tenta Grun. var. biceps V. Heurck, N. cryptocephala Kiitz., 

 N. falaisensis Breb., N. major Kiitz., N. jjeref/rma Kiitz. var. 

 Menisculus Schum., A', rliynchocephala Kiitz., N. s'tauroptera Grun., 

 N. tuscula Ehrenb., N. viridis Kiitz., Stauroneis anceps Ehrenb., 

 S. gracilis Ehrenb., Vanheurchia vulgaris (Thw.) V. Heurck, 

 Gomphonema parvulum Kiitz., Cocconeina turgidum (Greg.) nob. 

 [= Cymbella turgida Greg.] , Nitzschia Denticula Grun., N. obtusa 

 W. Sm., N. obtusa var. brevissima Grun., A''. Palea (Kiitz.) W. Sm. 

 var. debilis V. Heurck, Hantzsclna aviphioxys (Ehrenb.) Grun. 



Myxophyce^. — Phormidium tenue (Menegh.) Gom., Oscilla- 

 tor ia animalis Ag., 0. tenuis Ag. 



II. — A Diatomaceous Earth from Lewis, Outer Hebrides. 



Some three years ago Mr. F. J. Lewis, of the University of 

 Liverpool, forwarded me a sample of a Diatomaceous Earth which 

 he had collected to the south of Monach, near Loch Keiter, in 

 Lewis, and recently he has very kindly supplied me with the 

 particulars of its occurrence. The deposit was about 6 or 7 in. in 

 thickness, and was overlaid (1) by a layer of peat from 2J to 3 ft. 

 in thickness, containing trunks and stools of Betula alba, and 

 (2) by some 7 to 9 ft. of peat, derived from Scirpus lacustris and 

 Sphagnum. 



The deposit, which rested upon a few inches of fine sand on 

 rock, is soft and friable, and of a rather dark grey colour. It is a 

 fairly pure Diatomaceous Earth of freshwater origin, consisting of 

 a number of species, two of which stand out conspicuously from 

 the remainder. These two species occurred in great quantity and 

 about equal proportions, and not only are they much the largest 

 species present in the deposit, but are among the biggest of fresh- 

 water Diatoms. They are Surirella robusta Ehrenb. and Navicula 

 nobilis Ehrenb. var. Dactylus (Ehrenb.) V. Heurck. 



x\mong the large Diatoms were numerous acicular sponge- 

 spicules. 



The matrix of smaller Diatoms consisted of the following 

 species :—Tetracyclus lacustris Ealfs var. emarginatus (Ehrenb.) 

 W. Sm., Tabellaria fenestrata (Lyngb.) Kiitz., Fragilaria capucina 

 Desmaz., F. construens (Ehrenb.) Grun. var. binodis Grun., Eunotia 

 pectinalis (Kiitz.) Eabenh. var. undulata Ealfs, E. prarupta Ehrenb. 

 var. bidens (Ehrenb.) Grun., E. robusta Ealfs var. tetraodon 

 (Ehrenb.) V. Heurck, E. Veneris Kiitz., Navicula major Kiitz., 

 N. viridis Kiitz., Stauroneis Phanicenteron Ehrenb., Gomphonema 

 acuminatum Ehrenb., G. constrictum Ehrenb., G. intricatum 

 Ehrenb., Cocconema delicatulum{Ki\t'A.) nob. [= Cymbella delicatula 



