W. West and g. s. west: alga-flora of Yorkshire. lit 



Length of cells 7-5 — 9/*; breadth of cells 4/x; length of 

 spines 2 — 2 '5 /a. 



578. Scenedesmus Hystrix Lagerh. 

 S.E. — Skipwith Common. 



This species has not previously been recorded for the British 

 Isles. 



579. Scenedesmus acutiformis Schroder. 

 Mid W. — Staveley Dam, near Knaresborough. 



N.E. — Near Rievaulx Abbey. Pilmoor, near Tiiirsk. Malton. 



580. Scenedesmus costatus Schmidle. 

 N.E. — Pilmoor, near Thirsk (vii. 1898). 



This species was described by Schmidle (Oeslerr. bqtan. 

 Zeitschrift, 1895, p. 6 (Sep.), t. xiv., f. 5) from the Alps. 

 It has not previously been recorded for the British Isles. 



Genus RHAPHIDIUM Kiilz., 1845. 



581. Rhaphidium polymorphum Fresen. 



Var. falcatum (Corda) Rabenh. [Syn. R. falcatum\ 



S.W. — Bradford. CuUingworth. Keighley Moor. 



Mid W. — Baildon Moor. Chapel- Allerton ; Adel (J. Abbott). 

 Wigton Moor. Ilkley (VV. J. Dikes). Bolton Woods. Cocket 

 Moss, near Giggleswick. Penyghent. Harrogate. Boston Spa. 

 Staveley Dam, near Knaresborough. 



N.W.— Cronkley Fell. 



N.E. — Strensall ! (AV. B. Turner). Near Rievaulx Abbey, 

 Stokesley. Scarborough Mere. 



S.E. — Riccall and Skipwith Commons. 



Var. aciculare (A. Br.) Rabenh. [Syn. R. aciculare A. 

 Br.; Closteriu7n subtile '2>x€o.; CI. Griffithii ^txk.\ 



S.W.— CuUingworth! (T. Hebden). 



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

 Wigton Moor. Penyghent. Boston Spa. Brearton, near Knares- 

 borougl). 



N.VV. — Masham. Near Jervaulx Abbey. Muker. 



N.E. — Scarborough ]\Iere. ScalbyBeck. Malton. Stokesley. 



S.E. — Skipwith Common. 



