STAURASTRUM. 151 



IRELAND.- -Lough Gartan and near Lough Magrath, 

 Donegal ! Ballvnahinch, Galway ! 



Geogr. Distribution. Scandinavia. Java (var.). Azores. 

 United States. 







This characteristic little species is closely allied to St. tetracerum 

 Ealfs, from which it is readily distinguished by the protuberance 

 in the centre of each face of the semicell. 



145. Staurastrum Arachne Ealfs. 

 (PI. CL, fig. 1.) 



Arachne Kali's, in Ann. Mag. Xat. Hist. vol. 15, 1845, p. 157, 

 t. 11, f. 6; Brit. Desm. 1848, p. 13(3, t. 23, f. 6; Arch, in Pritck. Inf. 

 1801, p. 744 ; Pxabenh. Krypt.-ti. Sachs. 18(53, p. 191 ; Flor. Europ. Alg. 

 18(58, p. 210; Lund. Desm. Suec. 1871, p. (59 ; Kirchn. Alg. Schles. 

 1878. p. 168 ; Turn. Alg. Strensall Common, 1883, f. 20 ; Wolle, Desm. 

 U. S.' 1884, p. 129, t. 42, f. 38-42 ; Bpldt, Sibir. Chloroph. 1885, p. 118 ; 

 Cooke, Brit. Desm. 1887, p. 182, t. 63, f. 4 ; Xordst. Desm. Bornholm, 

 1888, p. 206 ; De Toni, Syll. Alg. 1889, p. 1229 ; West, Alg. W. Ireland, 

 1892, p. 187 ; Roy & Biss". Scott. Desm. 1893, p. 1(5 ; West & G. S. West, 

 Desm. U. S. 1898, p. 316 ; Cushmau in Pvhodora, v. 7, 1905, p. 201 ; 

 West & G. S. West, Brit. Kreshw. Phytoplankton, 1909, p. 203. 



Goniocystis (Pentasterias) Ara<-hne Mass. Brit. Alg. 1845, p. 355, t. 85, f. 8. 



Phycastnim Arachne Kiitz. Spec. Alg. 1849, p. 181. 



Ph. (Stenactinium) AracJnn Xa!_ f . <Jatt. -inz. Alg. 1849, p. 128. 



Cells small, about twice as broad as long, including 

 the processes, deeply constricted, sinus acute ; semicells 

 cup-shaped, ventral margin strongly ventricose. dorsal 

 margin nearly straight or slightly convex, upper angles 

 produced to form long slender processes, nearly as long 

 as the cell itself, each process tipped with about 3 minute 

 spines, and rough with numerous concentric series of 

 granules. Vertical view usually 5-angular, angles pro- 

 duced to form long processes, sides concave, sometimes 

 with a few scattered granules just within each lateral 

 margin between the processes. 



Zygospore unknown. 



Length 26 \L ; breadth, without processes, about 16 \i ; 

 with processes, 40-55 [JL ; length of processes 14-18 \L ; 

 breadth of isthmus 8-9 \i . 



ENGLAND. Strensall Common, N. Yorks (W. B. 

 Turner). Thursley Common, Surrey ! New Forest, 

 Hants ! 



