STAUEASTRUM. 189 



G. S. West, Brit. Freshw. Alg. 1904, p. 172, f . 65 G ; West & G. S. West, 



Brit. Fresh\v. Phytoplankton, 1909, p. 175 ; Kaiser, Alg. Traunstein u. 



Chiemgau, I, 1914, p. 152. 

 ? Xanthidium articulatum Corda in Aim. de Carlsbad, 1840, p. 213, t. 5, 



f. 35. 



Phycastrum furcigerum Kiitz. Phyc. Germ. 1845, p. 138. 

 Didymodadon furcigerum Ralfs, Brit. Desm. 1848, p. 144, t. 33, f. 12 ; Delp. 



Spec. Desm. subalp. 1877, p. 174, t. 14, f. 24-27. 

 Aster oxaniJiium furcigerum Kiitz. Spec. Alg. 1849. p. 183. 

 Phycastrum (Amblyactinium) furcigerum Nag. Gatt. einz. Alg. 1849, p. 125. 

 (Staurastrum) furcigerum Reinsch, Alg. Frank. 1867, p. 170. 



Cells large, slightly longer than broad, excluding the 

 processes, deeply constricted, sinus acute, narrow at 

 first, then opening more widely ; semicells elliptical, 

 dorsal and ventral margins almost equally convex, 

 lateral angles produced into short stout processes, tipped 

 with two or three sharp spines, apex of semicell with an 

 upper series of processes, similar or perhaps slightly 

 shorter than the lower series, and projecting vertically 

 above them ; processes with concentric series of denti- 

 culations. Vertical view triangular (or up to 9-radiate), 

 lateral margins concave, angles somewhat inflated and 

 then produced into short processes ; apex with a 

 similar short process in each angle. Semicells with a 

 single chloroplast and a central pyrenoid. 



Zygospore spherical, with numerous spines which are 

 stouter at the base, and twice dichotomous at the apex. 



Length, without processes, 35-48 [Ji ; including pro- 

 cesses, 50-70 fz ; breadth, including processes, 45-68 JJL ; 

 breadth of isthmus 13-1 8 pi; diam. zygosp., without 

 appendages, 39 fz ; Avith appendages, 74 pi. 



ENGLAND. Plankton of Crummock Water and 

 Ennerdale Water, Cumberland ! Westmoreland, and in 

 the plankton of Brother's Water and Hawes Water ! 

 Lancashire ! (Ralfs). W. and N. Yorks (zygospores from 

 Pilmoor, N. Yorks) ! Cheshire (Ralfs). Essex ! Burnham 

 Beeches. Bucks ! Plankton of Bracebridge Pool, Button 

 Park, War wicks ! Worcs ! Berks (Griffiths). Surrey ! 

 Sussex (Ralfs). Hants ! Dartmoor, Devon (Harris). 

 Cornwall ! (Marquand). 



WALES. Capel Curig, Carnarvon ! (Cooke & Wills). 

 Dolgelly, Merioneth (Ralfs). In the plankton ! 



