552 MR. W. WEST AND PROF. G. 8S. WEST ON 
Hab. Loch Shin, Sutherland. Lochs Katrine and Achray, 
Perthshire. 
This variety has not been previously recorded from the British 
Islands. 
Genus Desmtipium, Agh. 
38. D. eraciricers, Lagerh. in Ofvers. af K. Vet~Akad. 
Forh. (1885) no. 7, p. 228—D. quadratum, WNordst., var. 
graciliceps, Nordst. 1880. 
Long. 238-25 x; lat. 25-27; lat. apie. 95-11 yp; lat. isthm. 
18°5-20 p. 
Hab. Loch Nan Eun, N. Uist, Outer Hebrides. 
This species was in comparative abundance, and has not 
previously been recorded from the British Islands. We have 
also observed it from Sutherland. 
Order Protococcoidex. 
Family ProrococcacEea, 
Genus Sorastrrum, Kitz. 
39. S. amertcanum, Schmidle——Selenospherium americanum, 
Bohlin, in Bih. till K. Sv. Vet.-Akad. Handl. Bd. xxiii. (1897) 
no. 7, p. 40, t. 2. ff. 38-41. 
Diam. coenob. (¢. corn.) 55-61 »; diam. cell. 11°5-15 p. 
Hab. Loch Nan Eun, N. Uist, Outer Hebrides. 
Genus TETRAHEDRON, Kiitz. 
40. T. cructatum, West & G. S. West, in Botanisk Tidsskrift, 
Bd. xxiv. (1901) p. 99; Trans. Linn. Soc., ser. 2, Bot. vi. (1902) 
p- 198.—Micrasterias cruciata, G. C. Wall. in Ann. Mag. Nat. 
Hist. ser. 3, v. (1860) p. 281, t. 13. f. 12. Staurophanum 
eruciatum, W. B. Turn. in Kongl. Sv. Vet.-Akad. Handl. xxv. 
(1893) no. 5, p. 159, t. 20. ff. 20, 21. 
(a) Forms with each angle subdivided and somewhat irregular. 
Diam. 42-49 p. 
Hab. Lech Doon, Ayrshire. 
(6) Smaller forms, very little irregular. 
Diam. 34-38 p. 
Hab. Loch Mor Bharabhais, Lewis, Outer Hebrides. 
