Freshivater Algse of North Wales. By Wm. West. 291 
G. excavatum Nord. (Desm. Brasil., tab. iii. fig. 25), I propose the 
present suggestive name. A figure of the preceding species is given 
for comparison with this one. C. 
C. moniliforme Turp. S. 
G. contractum Kirch. C. 
G. glohosum Buln. A., S. 
Genus Galocijlindrus De Bary. 
G. cylindricus Ralfs. P. 
G. 'pseudoconnatus Nord. B. 
G. cucurhita Breb. Frequent. 
G. palangula Breb. C. 
G. Thwaitesii Kalfs. D. 
G. curtus Breb. C., B., F. 
G. Be Baryi Arch. C. 
G. stra7igulatus Cooke & Wills. C. 
Genus Xantliidium Ehrb. 
X. ar7natu77i Breb. P., D., A., S. 
X. aculeatum Ehrb. Do., P., S. 
Long. 74 /X ; lat. 62-75 /x ; from Snowdon. 
Long. 64 /X ; lat. 62 /x ; crass. 28 /x ; from Llyn Padarn. 
A peculiar form of this is figured, which some may think belongs 
to the next species by reason of the shape of the basal angles of the 
semicells ; still the spines are scattered in the same way as those of 
the species under which it is placed. Fig. 39. 
X Brehisso7iii Kalfs. P. 
Fig. 38 represents a form which differs from that usually seen. 
X. aTfitilopeuTfn Breb. C., P., Do. 
Large forms of this species were seen from Capel Curig up to 
78 /X in diameter. 
X. cristatum Breb. var. spinuliferum nov. var. Fig. 21. 
Var. cum quattuor vel quinque spinis parvioribus additis 
insequaliter ordinatis intra marginem semicellulae singulae. 
This has from four to five additional spines rather unequally 
disposed just within the margin of the front view of each semicell. C. 
Genus Arthrodesmus Ehrb. 
A. octocornis Ehrb. S. 
A variety with wide and short cells is figured. Fig. 40. 
A. i7iC7is Hass. var. convergens Arch. C. 
var. diver geTfis ArcL C., F. 
