SMITH: ALGAE FROM THE LAKES OF WISCONSIN 479 
Lankester states that the genus Archerina antedates Richter- 
iella. There is no question of the identity of the two organisms, 
f. 21 of Lankester’s plate being especially characteristic. In the 
material studied by Lankester he mistook a naked amoeboid 
parasite investing the plant cells for an integral part of the or- 
ganism and so considered Archerina a protozoan and not an alga. 
The name Richteriella cannot be retained in any Case, since those 
who regard the description of Micractinium as being too vague ~ 
should use Archerina in its place. 
This alga, which I have found in abundance in some of the 
local lakes, at times forms large irregular colonies containing over a 
thousand cells. The most common state, however, is the flat 
plate of sixteen cells with an open central space, the form afenestrata 
Chodat. This name and also the form-name fetraedrica Lem- 
mermann are unwarranted since they may both occur in the same 
colony. 
Micractinium quadrisetum (Lemm.) comb. nov. 
Richteriella quadriseta Lemm. Hedwigia 37: 307. pl. 10, f. 7. 1898. 
Richteriella botryoides var. quadriseta Chodat, Matér. pour la 
Flore Crypt. Suisse 1°: 194. 1902. 
PLATE 25, FIG. 17 
DISTRIBUTION: plankton, Catfish and Cranberry Lakes. 
The character on which the specific name is based, that of four 
spines, is not constant enough to warrant the establishment of a 
separate species. It is probably on this account that several in- 
vestigators have followed Chodat’s lead and considered it a form 
hardly worthy of naming. On the other hand the cell is always 
distinctly ovoid in this species, whereas it is always spherical in 
M. pusillum. The cell-dimensions in M. quadriseta are also 
always constantly larger. Since there are these differences M. 
guadriseta should be considered a distinct species. 
Tetraedron planctonicum sp. nov. 
Cells four- or five-sided, sides generally incurved and equal. 
Angles of cells prolonged into bifurcate or trifurcate processes 
ending i in two or three horns. Processes broad in top view, narrow 
in side view. 
