THE GENUS TETRAPEDIA. j ."» 



isionally) to record them under Reinsch's genus, if indeed that 

 observer may not consider it unallowable so far to modify the terms 

 thereof as to admit of its embracing the two new forms. It may 

 be objected that the very name of the genus would preclude the 

 admission of a ^^e-lobed form into it, but the name Staurastrum 

 is retained though only a minority of the forma referable thereto 

 are cruciate or quadrangular in end view, so also with Triceratium, 

 where four and live-angled forms occur, &c. I venture, therefore, 

 to cast the description of these forms as follows: — 



Tetrapedia (Reinsch) mut. quodammodo char. 

 Cells compressed, quadrangular or triangular, equilateral, be- 

 coming 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. Reinsch. — 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 after- 

 wards also deeply incised ; each of the sixteen (secondary) roundly 

 angled quadrate segments thus produced becoming equal in dimen- 

 sions to the original cell, and their lateral margins emarginate at 

 the middle (whereat afterwards incised ?) ; all the incisions per- 

 pendicular 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 in- 

 cisions 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. [PI. iii. figs. 1-7.] Diameter 

 of single cell about TT ^ to -^ T ". 



In a ditch and in a mill-race (scantily) near Erlangen. 



It seems to be probable that another distinct form exists — that 

 figured by Reinsch (op. cit. t. ii. f. 2. i.), and reproduced in our 

 plate [PI. iii. f. 8]. Should that form recur to him, probably he 

 may be in a position to throw further light on it on a future occa- 

 sion. 



Tetrapedia Crux-Michaeli. Reinsch. — Cells quadrate, lateral 

 margins entire, with two shallow concavities, each extending half 

 the length of the side, thus producing an obtuse-angled central 

 prominence, deeply incised at the angles, incisions diagonal, recti- 

 lineal, dee}), acute below, slightly expanding upwards, thus bisect- 

 ing the angles, and dividing the cell into four broadly cuneate seg- 

 ments, the upper angles of which are subacute (the incisions ulti- 

 mately completed, and the cell breaking up?) ; in side view lanceo- 

 late, ends acute. [PI. iii. f. 9-10.] Diameter of cell about 



In running water (very scantily) near Erlangen, also (very 

 scantily) near Mullingar, Co. Westmeath, Ireland. 



