110 BRITISH DESMIDIACEJ:. 



the semicells are minutely lobecl (or granulated) ; with 

 about four smaller and somewhat indistinct protuber- 

 ances completing the transverse row across the base 

 of the semicell; four smaller protuberances are also 

 subradiately disposed on the polar lobe, five on each 

 of the upper lateral lobes, and two on each of the 

 lower lateral lobes, but the number of these protu- 

 berances is subject to variation. 



Zygospore unknown. 



Length 210 /x; breadth ISO jit; breadth of isthmus 

 29 p,. 



SCOTLAND. - -Collieston, Bennachie, Powlair in Birse, 

 Slewdrum, Aboyne, Birsemore Loch, Moss of Logie, 

 Morven, and Dalbagie, Aberdeen ; Craithes near Ker- 

 loch, Kincardine (Roy $ Bissett). Loch Ness, Inver- 

 ness ! (./. Murray). 



Geogr. Distribution. United States. 



We have not seen this species, but Mr. James Murray 

 submitted a drawing for our inspection of a specimen of 

 Micrasterias from Loch Ness which could certainly be referred 

 to M. verrucosa. 



Roy and Bissett state that "it is not granulated in the 

 ordinary sense ; the prominences seem flattened, and their 

 margins cut into rounded segments, similar to the stigma of 

 a species of Poppy, only more deeply cut." 



14. Micrasterias Thomasiana Arch. 

 (PL LI, figs. 3-6.) 



Micrasterias Thomasiana Arch. Description of a new Species of Micras- 

 terias, etc., Proc. Dubl. Nat. Hist. Soc. 1862, p. 72, t. 2, f. 1-5 ; Journ. 

 Micr. Soc., new ser., II, 1862, p. 239, t. 12, f . 1-5 ; Rabenh. Flor. Europ. 

 Alg. Ill, 1868, p. 192 ; Joslma in Journ. Bot. 1882, p. 301 ; Cooke, Brit. 

 Desm. 1886, p. 58, t. 25, f . 1 (in part) ; West, Alg. W. Ireland, 1892, 

 p. 134 ; Alg. Eng. Lake District, 1892, p. 722 ; Roy & Biss. Scott. Desm. 

 1893, p. 174 ; Nordst. Index Desm. 1896, p. 254 ; West & G. S. West, 

 Desm. Singapore, 1897, p. 163; Alg. S. England, 1897, p. 484; G. S. 

 West, Variation Desm. 1899, p. 384, t. 9, f. 6-8 ; West & G. S. West, 

 Alga-fl. Yorks. 1900, p. 67 ; Alg. N. Ireland, 1902, p. 30. 



IH. denticulata Breb. forma Thomasiana Jacobs. Desm. Danem. 1875, 

 p. 187. 



Helierella Thomasiana Kuntze, Eevis. gen. plant. 1891, p. 899. 



Cells rather large, suborbicnlar, very deeply con- 

 stricted, sinus narrowly linear ; semicells 5-lobed, 



