New British Freshwater Algse. By William West. 9 
Long, sine spin. 80-82 /z ; long, cum spin. 105-115 /x ; 
lat. sine spin. 62-63 /z : lat. cum spin. 85-100 /z ; lat. isthrn. 
21-25 fi. 
Hab. Derrycrow Bog, near Lurgan, N.E. Ireland (H. W. 
Lett). 
This also somewhat approaches f. evolutum Lutk. (Desmid. aus 
der Umgeb. des Atters. in Oberdstr., p. 12) but differs in its much 
larger size and in its longer and more irregularly disposed spines. 
Genus Arthrodesmus Ehrnb. ; Arch. 
A. convergens Ehrnb. 
Forma memhrana irregulariter punctata. 
Long. 50 fi ; lat. sine spin. 50 fi ; lat. cum spin. 62 /z. 
Hab. Corrie Ceandor, Scotland. 
A bifidus Breb. var. truncatus West (Freshw. Alg. of N. 
Yorks, in Journ. Bot., Oct. 1889, tab. 291, fig. 9). f. 
sucoisa. Fig. 52. 
Forma angulis superioribus truncatis vel levissime emargi- 
natis. 
Long. 12 ’5 /z ; lat. 11*5 fi ; lat. istbm. 3 /z ; crass. 6 /z. 
Hab. Bowness, Lake District. 
A. controversy sp. n. [ = A. ? glaueeseens Wittr. f. convexa 
West, Freshw. Alg. of W. Ireland, p. 170, pi. xxii. fig. 10 ; 
Freshw. Alg. of Eng. Lake District, p. 730, pi. ix. fig. 27. 
Non A. ? glaueeseens Wittr., Om Gotl. och 01. Sotvat. Alg., 
p. 55, t. 4, f. 11 (= Tetrapedia glaueeseens (Wittr.) Boldt, 
Stud. ofv. Sotvattens-alg. och der. Utbredn., 1888, p. 59)]. 
A. minutus, paullo longior quam latior (sine spin.) modice 
constrictus, sinu obtusangulo et amplissimo extremo sub- 
acuminato ; semicellulae cuneatse cum lateribus et apicibus 
convexis, angulis superioribus spinis brevibus delicatis ornatis ; 
a vertice visae circulares ; membrana glabra. 
Zygosporse globosae, aculeis simplicibus longis ornataeN 
Long. 12 /z ; lat. sine spin. 10 /z ; lat. cum spin. 12*5 /z ; 
lat. istbm. 5 /z ; crass. 6 • 5 /z ; diam. zygosp. sine spin. 16*5 /z, 
cum spin. 29 /z. 
Hab. Creggan Lough, Co. Mayo, and Adrigole, Co. Cork, 
in Ireland. Hawkshead and Wastdale (c. zygosp.) in Lake 
District. 
Wittrock (l.c.) described a plant as Arthrodesmus ? glaueeseens ; 
this has since been relegated to the genus Tetrapedia. I described as a 
form (f. convexa ) of this plant, an Arthrodesmus of very similar form 
and dimensions ; this having zygospores cannot be a Tetrapedia , but 
is undoubtedly a desmid and is therefore described under the above 
name. 
