36i WILLIAM ARCHER. 



Tetrapedia gothica (Reinsch). 



Cells quadrate, angles rounded, lateral margins eniarginate 

 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 perpendicular to the sides, rounded below, 

 somewhat wide, of an equal average width throughout; 

 ultimately a quadrate foramen through the cell at the central 

 jjoints 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. 

 Figs. 1 to 7. Diameter of single cell about -^-Vt ^o jnVT"- 



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 repro- 

 duced 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 Crux-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 in- 

 cised at the angles, incisions diagonal, rectilineal, deep, acute 

 below, slightly exj^anding upwards, thus bisecting the angles 

 and dividing the cell into four broadly cuneate segments, the 

 iqiper angles of which are subacute (the incisions ultimately 

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

 late, ends acute. 



Figs. 9, 10. Diameter of cell about ^-tW to „ ^'g ^ ." 



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

 scantily) near Mullingar, Ireland. 



Tetrajjedia Reins chiana, no v. sp. 



Cells quadrangular, two opposite margins excavated by a 

 wide triangular sinus, thus subdividing the cell into two 

 broadly cuneate segments, connected by a wide isthmus, and 

 » Op. cit., t. II, fig. ii, i. 



