W. WEST AND G. S. WEST: ALGA-FLORA OF YORKSHIRE. 12 1 



Length of cells 7*5 — g fj-, breadth of cells 4 /x ; length of 

 spines 2 — 2'5 /x. 



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 Tirirsk. Malton. 



580. Scenedesmus costatus Schmidle. 

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



This species was described by Schmidle (Oesteir. botan. 

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

 It has not previously been recorded for the British Isles. 



Genus RHAl'lIIDIl'M Kiiiz., 1845. 



581. Rhaphidium polymorphum Fresen. 



Var. falcatum (Corda) Ral)enh. [Syn. R. fakatuni\ 



. S.W. — Bradford. CuUingvvorth. Keighley Moor. 



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

 ■Wigton Moor, Ilkley (W. J. Dikes). Bolton Woods. Cocket 

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

 Staveley Dam, near Knaresborough. 



N.W.— Cronkley Fell. 



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

 Stokesley. Scarborough Mere. 



S.E. — Riccall and Skipwith Commons. 



Var. aciculare (A, Br.) Rabenh. [S)n. R. ackulare A. 

 Br.; ClosteriiDii subtile ^\€o.; CI. Griffitliii ^ktx\\ . 



S.W.— Cullingworthl (T. Hebden). 



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

 ^Vigton Moor. Penyghent. Boston Spa. Brearton, near Knares- 

 borough. 



N.\V. — Masham. Near Jervaulx Abbey. Muker. 



N.E. — Scarborough Mere. Scalby Beck. JNIalton. Stokesley. 



S.E. — Skipwith Common. 



