Archer — On the Genus Tetmpedia. 
307 
and so on. I venture then to cast the descriptions of these forms as 
follows: — 
Class, Phycochromacese. 
Family, Chroococcacese. 
Genus, Tetrapedia (Reinsch) mut. quodammodo char. 
Cells compressed, quadrangular or triangular equilateral, becoming 
subdivided into quadrate or cuneate segments or rounded lobes, either 
by deep vertical or oblique incisions, or by wide angular or rounded 
sinuses. 
Tetrapedia Gothica (Keinsch). 
Cells quadrate, angles rounded, lateral margins emarginate at the 
middle, whereat afterwards deeply incised ; each of the four roundly- 
angled quadrate segments thus produced becoming equal in dimensions 
to the original cell, and their lateral margins emarginate at the middle, 
whereat afterwards also deeply incised ; each of the sixteen (secondary) 
roundly- angled quadrate segments thus produced becoming equal in 
dimensions to the original cell, and their lateral margins emarginate at 
the middle (whereat afterwards incised?); all the incisions perpendi- 
cular to the sides, rounded below, somewhat wide, of an equal average 
width throughout ; ultimately a quadrate foramen through the cell at 
the central points of junction of the segments (the incisions afterwards 
completed and the segmented tablet breaking up ?). In side view the 
single cell oblong, at the middle slightly concave at each side, ends 
rounded. 
Plate XXI., Figs. 1 to 7. Diameter of single cell about ^^-^^ to 
1 M 
3 12 5 • 
In a ditch, and in a mill-race (very scantily) near Erlangen. 
(It seems to be probable that another distinct form exists, as above 
referred to, that figured by Reinsch"^' and reproduced in accompanying 
figure (fig. 8). — Should that form recur to him, probably he may be in 
a position to throw further light on it on a future occasion). 
Tetrapedia Orux-Michaeli (Reinsch). 
Cells quadrate, lateral margins entire, with two shallow concavities, 
each extending half the length of the sides, thus producing an obtuse- 
angled central prominence, deeply incised at the angles, incisions dia- 
gonal, rectilineal, deep, acute below, slightly expanding upwards, thus 
bisecting the angles and dividing the cell into four broadly cuneate 
segments, the upper angles of which are sub-acute (the incisions ulti- 
mately completed and the cell breaking up ?) ; in side view lanceolate, 
ends acute. 
* Op, cit. t. II. fig. II. i. 
