bo 
MR. G. S. WEST ON SOME CRITICAL GREEN АІС Ж. 87 
The outward form of this Tetracdron recalled to my memory опе of 
Areher's preliminary notes on a supposed new species of Desmid'. This 
brief preliminary account, like many others by the same writer, was un- 
fortunately never followed by the promised detailed description. It is 
copied by Cooke ?, and reads as follows :— 
“ Cosmarium platyisthmum, Archer. Minute. In general outline in front, 
or broad view, much resembling, say, a section of a double railway-rail—that 
is to say, the isthmus very broad and comparatively long, thus the isthmus 
makes up a great proportion of the whole Cosmarium ; the semi-cells are 
elliptic, much broader than high, the whole smooth: end view elongate 
compressed, extremities rounded. The lateral extremities of the semi-cells 
somewhat taper ere becoming rounded off, and the upper margins are notably 
retuse in the middle, Size not given. Mab. Ireland." 
A comparison of the above description with the specimens from Scotland 
leaves no doubt as to the identity of the Irish and Scottish plants. As a 
further confirmation of this view, | may add that many of Archer’s new 
species were collected in Connemara, and that the Alga-flora of West Ireland 
very closely resembles that of North-West Scotland. The similarity between 
the species occurring in certain districts of Connemara and those found in 
Western Sutherland is most striking. In fact, so far as their British distri- 
bution is concerned, many of them are only known to occur in these two areas. 
Archer was in error in referring the plant to the Desmidiaeem аха species of 
the genus Cosmarium, and he omitted to mention certain of its characteristic, 
although inconspicuous features. 
б. CHODATELLA QUADRISETA, Lemmermann. (Pl. 21. figs. 40-43.) 
This genus Chodatella belongs to the subfamily Phytheliew of the Proto- 
coccaceæ (or Autosporacem), and was founded by Lemmermann ? to include 
a number of free-Hoating unicells, furnished with long spines. 
It is very closely allied. to Lagerheimia, Chodat, differing only in the 
absence of tubercles at the base of the spines. Lemmermann enumerates 
seven species known up to 1898. Three of these— C. ciliata, (Lagerh.) Lemm., 
C. amphitricha, (Lagerh.) Lemm., and С. radians. (West) Lemm.—«hould 
clearly be united, reducing them to five, and another species discovered in 
[902 makes a total of six known species. 
Although many of the Alge comprising the Phythelieze are constituents of 
the freshwater plankton, my recent experience is that they occur more 
frequently in the waters of small ponds such are found on old pasture-land. 
being intermingled with other free-floating Protococcaces of the genera 
Ankistrodesmus, Scenedesmus, Tetraédron, &c. 
| W. Archer in Journ, Dubl. Mier, Club, iv. (1880-5) р. 27. 
” M. C. Cooke, Brit, Desm, 1886-7, р. 187. 
' E. Lemmermann in Hedwigia, xxxviii. (1898) p. 309, 
