W. WEST AND G. S. WEST : ALGA-FLORA OF YORKSHIRE. I43 

 Genus APHANIZOMENON Morren, 1838. 



708. Aphanizomenon Flos-aquae (L., 1753) Ralfs, 



1850. 

 N.E. — Strensall Common. 



A form a little smaller ; cfr. West, Notes on F. W. A. of E. 

 Yorks. (Naturalist, July, 1893, p. 217). 

 S.E. — Riccall Common. 



Genus CYLINDROSPERMUM Kiitz., 1843. 



709. Cylindrospermum stagnale (Kiitz., 1843) Born 

 at Flah., 1888. [Syn. Anabcena stagnalis Kiitz., 

 1843; Cylindrospermum macrospermim Kiitz., 1845]. 



Mid W. — Ribblehead, in peaty ditches and pools. Staveley 

 Dam, near Knaresborough. 

 N.E. — Pilmoor, near Thirsk. 



710. Cylindrospermum majus Kiitz., 1843. [Syn. 



Cylindrosfermiiin macrospermum Rabenh., i860; 

 Cooke, Brit. Freshw. Alg., p. 243, t. 95, f. i]. 

 S.W. — Bradford. Halifax. Dewsbury (W. Narramore). Don- 

 caster! (Rev. W. Fowler). 

 N.E. — Terrington. 



711. Cylindrospermum catenatum Ralfs, 1850. 

 S.W.— Goole (W. G. Tacey). 



Mid W.— Markington ! (Rev. J. S. Tute). 



Sub-Order HOMOCYSTE^. 



Family VAGINARIE^. 

 Genus SCHIZOTHRIX Kutz., 1843. 



712. Schizothrix Miilleri Nag., 1849. 



Mid W. — Forming a brown expanded stratum amongst mosses 

 on wet rocks, Linn Gill. 



713. Schizothrix lardacea (Cesati) Gomont. 



Mid W. — Amongst Scytonema myochrous, forming a dense 

 stratum, Cowside Beck, Arncliffe. 



This species has not previously been recorded for the British 

 Isles. 



