287 



THE PHYTOPLANKTON OF THE ENGLISH 

 LAKE DISTRICT. 



Wm. west, F.L.S., 



AND 



G. S. WEST, M.A., D.Sc, F.L.S. 



[Contimied from page 267). 



6. MiCRASTERIAS MAHABULESHWARENSIS Hobson var. 



Wallichii (Grun.) W. & G. S. West, 1. c. p. 122, t. 54, f. 7, 8 ; 

 t. 55, f. 1-3. M. Wallichii Grun. 



This interesting Desmid occurred in the plankton of Gras- 

 mere. In the British Islands it was only previously known from 

 the plankton of certain of the lochs of Scotland and the Shetland 

 Islands, in which places it has recently been discovered. Long. 

 197 /X ; lat. 150-165 /A ; lat. isthm. 32 /x. 



7. CosMARiUM CONTROVERSUM Wcst in ' Journ. Roy. 

 Micr. Soc.', 1890, p. 289, t. 6, f. 31 [both description and figure 

 imperfect]. 



This rare species has previously been recorded from both 

 Wales and Scotland. It occurred in the plankton of Grasmere, 

 but was very rare. The following is an amended description of 

 the species : — 



G. submagnum, i^-ij-plo longius quam latum, profunde 

 constrictum, sinu angusto-lineari extremo ampliato ; semi- 

 cellulae pyramidato-trapeziformes, angulis basalibus rotundatis, 

 lateribus leviter convexis, angulis superioribus rotundatis, 

 apice late truncato ; a latere visae ovato-ellipticse ; a vertice 

 visae ellipticae, tumore Darvo a d medium utrobique. Membrana 

 granulata, granulis rotundatis et uniformibus, in series obliquis 

 decussatis 14 et series verticalibus indistinctis 18-19 (nonnun- 

 quam vix conspicuis), ad marginem semicellularum uniuscu- 

 j usque granulis 30-35 visis, in centro semicellularum cum 

 scrobiculis rotundatis conspicuis inter granulos. Pyrenoidibu? 

 binis. 



Long. 90-96 /X ; lat. 72-77 fx ; lat. isthm. 22-32 /x ; 

 crass. 45 fj^. 



8. Arthrodesmus triangularis Lagerh. var. subtrian- 

 GULARis (Borge) W. & G. S. West in ' Trans. Bot. Soc. Edin.', 

 XXIII., 1905, p. 24. A. Incus var. subtriangularis Borge in 

 ' Botaniska Notiser,' 1897, p. 212, t. 3, f. 4. A. triangtilaris 

 var. hebridamm W. & G. S. West, * Journ. Linn. Soc.', XXXV 

 1903. P- 542. 



1909 Aug. I. 



