W. WEST AND G. S. WEST : ALGA-FLORA OF YORKSHIRE. I47 



728. Phormidium valderianum (Delp., 1857) 

 Gomont, 1893. [Syn. Leptothrix Valdedce Delp., 

 1857; Hyphczothrix zonata (Ces.) Rabenh., 1865. 



Mid W. — On the shady boulders of rapid stream, forming a 

 thin dark olive-green stratum ; Holden Gill, near Keighley. 

 Thickness, trichome, 2 — 2-3 yu, ; long, artic. 3-5 — 5 \i-. 



729. Phormidium laminosum (Ag., 1827) Gomont, 



1890. [Syn. Oscillatoria laminosa Ag., 1S27]. 

 Mid W. — On stones in stream, Langcliffe, near Settle. 

 N.W. — Helln Pot, near Selside. 



730. Phormidium tenue (Menegh., 1837) Gomont, 



1893. [Syn- Anabcena tenuis Menegh., 1837. 

 S.W. — Cragg Vale, towards Blackstone Edge. Clayton. 

 Mid W. — Shipley Glen. Boston Spa. 

 N.W.— Cautley Spout. 



731. Phormidium inundatum Kiitz., 1849. 



[Syn. Lyngbya inundata (Kiitz.) Cooke, 1884]. 



S.W.— Bradford. 



Mid W. — Not uncommon on dripping rocks, stones in 

 streams, lakes, etc. Wetherby. Chapel-Allerton. Selby. 

 Penyghent. 



732. Phormidium Corium (Ag., 1812) Gomont, 1890. 



[Syn. Oscillatoria Corium Ag., 181 2]. 

 S.W. — Horton Park, Bradford. Cragg Vale, towards 

 Blackstone Edge. 

 Mid W.— Linn Gill. 

 N.W. — On rocks, in stream. Little Ing Gill, Dodd Fell. 



733. Phormidium Retzii (Ag. 181 2) Gomont, 1890. 

 [Syn. Oscillatoria Retzii Ag., 181 2 ; Phormidium 

 rupestre Kiitz., 1849; Phormidium papyrinum Kiitz., 

 1843 'i Lyngbya rupestris (Kiitz.) Cooke, 1884]. 



Mid W. — Ingleton ! (H. F. Parsons). Blubberhouses 

 (W. B. Turner), Holden Gill, near Keighley. 



