STAURASTRUM. 161 



' 



1884, p. 140, t. 45, f. 1-3 ; Cooke, Brit. Desm. 1887, p. 174, t. 60, f. 2 ; 



Hansgirg, Prodr. Alg. Bohm. 1888, p. 215 ; De Toni, Syll. Alg. 1889, 



p. 1216 ; Anders. Sverig. Chlorophy. 1890, p. 12 ; Liitkem. Desm. 



Attersees, 1893, p. 568 ; Roy & Biss. Scott. Desm. 1893, p. 16 ; West & 



G. 8. West, Alg. S. England, 1897, p. 496 ; Schroder, Beitr. Algen Riesen- 



gebirge, 1898, p. 42 ; G. S. West, Variation Desm. 1899, p. 393, t. 11, 



f. 28-32 ; Liitkem. Desm. Millstattersees, 1900, p. 76 ; Comere, Desm. 



de France, 1901, p. 151, t. 11, f. 12 ; West & G. S. West, Brit. Freshw. 



Phytoplankton, 1909, p. 203. 

 Goniocystis (Trigonocy-stis) aculeata Hass. Brit. Freshw. Alg. 1845, p. 353, 



t. 84, f. 12. 

 Phycastrum aculeatum Kiitz. Phyc. Germ. 1845, p. 138 ; Spec. Alg. 1849, 



p. 182. 



Ph. (Stenactinium) aculeatum Nag. Gatt. einz, Alg. 1849, p. 128. 

 Didyrnidium (Staurastrum) aculeatum Reinsch, Alg. Frank. 1867, p. 176, 



(in part). 

 Staurastrum aculeatum var. Ehrenbergii Rabenh. Flor. Europ. Alg. 1868, 



p. 218. 



Cells of medium size, about as long as broad, or up 

 to Ijr times broader than long, deeply constricted, sinus 

 acute and open ; semicells subelliptical or subfusiform, 

 dorsal and ventral margins almost equally convex, 

 though the ventral margin is not infrequently slightly 

 more convex than the dorsal ; lateral angles slightly or 

 not at all produced, terminating in 3 or 4 strong spines 

 and sometimes with one or two series of denticulations 

 beneath ; apex of semicell with a dorsal series of spines, 

 the median ones being sometimes emarginate ; semicells 

 also with a lateral series of spines running horizontally 

 from angle to angle across the face of the semicell. 



O O 



Vertical view triangular or quadrangular, sides nearly 

 straight, angles scarcely produced, tipped with 3 or 4 

 strong spines ; lateral margins with a row of spines, and 

 with a dorsal series of spines just within each lateral 

 margin. 



Zygospore globose, furnished with long spines forked 

 or dichotomous at the apex (Lund.). 



Length 33-50 (JL ; breadth, including spines, 48-60 ^ ; 

 breadth of isthmus 12-16 (j.; diam. zygosp., without 

 spines, 44 \i ; length of spines, 18 [JL. 



ENGLAND. Wastdale, Cumberland ! Loughrigg ! and 

 Bowness !, Westmoreland (Ralfs). Hawkshead, Lanca- 

 shire ! Strensall, N. Yorks (W. B. Turner). Thursley 

 Common, Surrey ! Sussex (Ralfs). New Forest, Hants ! 



VOL. V. 11 



