AETHKODES M US . Ill 



spicuous difference in convexity between the ventral 

 and dorsal margins ; spines shorter and more slender. 



Length ol-o8/x,; breadth without spines ol-42/x, 

 Avith spines 52-65 /x ; long. spin. 10'5-11'5 ft ; breadth 

 of isthmus 8-12 p; crass. 16-19'5/x,. 



SCOTLAND.- -Plankton of Loch Xan Eun, X. Uist, 

 Outer Hebrides ! 



IEELAND.- -Longh Gartan, Donegal ! 



10. Arthrodesmus octocornis Ehrenb. 

 (PI. CXVII, figs. 0-10.) 



Arthrodesmus octocornis Elirenb. Infus. 1838, p. 152 ; Hass. Brit. Freshw. 



Alg. 18 15, p. 357, t. 85, f . 11 ; Arch, in Pritch. Infus. 1861, p. 736 ; Eabenh . 



Flor. Europ. Alg. Ill, 1868, p. 225 ; Lund. Desm. Suec. 1871, p. 55 ; 



Kirchii. Alg. Schles. 1878, p. 156 ; Wolle, Desm. U. S. 1884, p. 97, t. 24, f. 



22 ; Cooke, Brit, Desm. 1887, p. 134, t, 47, f . 2 ; De Toni, Syll. Alg. 1889, 



p. 1063 ; West, Alg. N. Wales, 1890, p. 291 ; Gutw. Flor. Gloii. Okolic 



Lwowa, 1891, p. 64 ; West, Alg. W Ireland, 1892, p. 167 ; Alg. Engl. 



Lake Distr. 1892, p. 730 ; Eoy & Biss. Scott. Desm. 1894. p. 41 ; Nordst. 



Index Desmid. 1896, p. 187 ; W. & G. S. West, Alg. S. England, 1897, 



p. 496, t. 6, f. 16 ; Schmidle Lappmark Siisswasseralgeii, 1898, p. 42 ; 



Liitkem. Desm. Millstattersees, 1900, p. 71 ; W. & G. "S. West, Alga-fl. 



Yorks. 1901, p. 109; Borg. Freshw. Alg. Faeroes, 1901, p. 229; W. 



& G. S. West, Alg. N. Ireland, 1902, p. 57; Liitkem. Zellnienibr. Desmid. 



1902, t. 18, f. 17 ; W. & G. S. West, Scott. Freshw. Plankton, I. 1903. 



p. 528 ; Larseii, Freshw. Alg. E. Greenland, 1904, p. 81 ; W. & G. S. 



West, Further Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 485 ; 



Borge, Beitriige Alg. Schweden, 1906, p. 49 ; Larsen, Ferskvaiidsalg. 



Vest-Gronl. 1907, p. 325; W.& G. S. West, Brit. Freshw. Phytoplankton, 



etc., 1909, p. 181; Hustedt, Desni. tt Bacill. aus Tirol, 1911, p. 336, 



f. 25. 



Micrasterias octocornis Menegh. Synops. Desm. 1840, p. 216. 

 Staurastrum ? octocorne Ealfs in Ann. Mag. ]S"at. Hist. 1845, xv, p. 159, 



t. 12, f. 3. 



Ei'astrnm octocorne Kutz. Phycol. germ. 1845, p. 134. 

 Xanthidium ? octocorne (Ehreub.) Ealfs, Brit. Desni. 1848, p. 116, t. 20, 



f. 2 a-e ; Archer in Q. J. Micr. Sci. 1869, p. 423 ; Gay, Monogr. loc. Conj. 



1884, p. 77 ; Him. Desm. Finland, 1903, p. 24. 

 Enastrum octacanthum Perty in Mittheil. d. iiaturforsch. Gesellsch. in 



Bern, 1849, p. 174. 



Didymidium (Xanthidium} octocorne Eeinsch, Algenfl. Frank. 1867, p. 127. 

 Xdatliidium octocorne forma minor Jacobs. Desm. Danem. 1876, p. 211. 

 Arthrodesmus Lapczynskii Gutw. Xonn. alg. nov. 1896, p. 57, t. 7, f. 68. 



Cells small, about 1-j- times longer than broad 

 (without the spines), deeply constricted, sinus a wide, 

 almost semicircular excavation ; semicells tranversely 

 trapeziform-rectangular, sides and apex concave, angles 

 slightly rounded and each furnished with one fairly 



