46 THE GENUS TETRAPEDIA. 



Tetrapedia Reinschiana. nov. sp. — Cells quadrangular, two op- 

 posite margins excavated by a wide triangular sinus, thus sub- 

 dividing the cell into two broadly cuneate segments connected by a 

 wide isthmus, and somewhat convex on their lower margins ; the 

 other two opposite margins of the cell, that is the upper margins of 

 the segments, very slightly concave at the middle, somewhat raised 

 towards the acute outer angles ; in side view oblong, constricted at 

 the middle, ends rounded. [Pl.iii. f. 11-13]. Diameter of largest 

 cell met with (from angle to angle in both directions equal) from 

 about 2T00"" to one-third, or even one half smaller. 



In moor pools, Co. Dublin and Wicklow. 



Tetrapedia setigera. nov. sp. — Cells triangular, the lateral margins 

 somewhat deeply excavated by a broad rounded sinus dividing the 

 cell into three lobes, rounded at the ends, and each terminated by 

 a very delicate straight bristle, in length about equal to the dia- 

 meter of the cell ; in side view oblong, somewhat inflated at the 

 middle at each side, ends rounded, and each seen tipped by the 

 bristle. [PI. iii. f. 14-17.] Diameter of cell (without bristles), 

 about 40V0 to 34V o"? from end to end, including the bristles about 

 1 + A 1 " 



1 sen V\J "1 1 6 * 



In moor pools, Co. Dublin and Wicklow. 



Reinsch' s figures are so much enlarged that they are calculated 

 to mislead. In the present plate they are reduced into uniformity 

 with our own to a scale of some 400 diameters. The descriptions 

 of his forms are a direct translation, somewhat altered in order, 

 from the original. 



PI. iii. f. 1, Tetrapedia goihica, Reinsch, a single developed cell, 

 whose lateral margin presents the indication of division. 



F. 2. A cell with the indication of division, the angles bluntly 

 rounded. 



F. 3. A cell [the division] somewhat more advanced. 



F. 4. A four-celled family, the [secondary] cells still connected 

 in the middle by the angles, the depth of the incisions almost their 

 breadth, the individual cells fully formed, i. e., already with the 

 commencement of a division into a new cell-generation, the margin 

 of the side-lobes of the [secondary] cells somewhat emarginate 

 at the middle. 



F. 5. A four-celled family, the tablet furnished in the middle 

 with a quadrangular hole (Loch). 



F. 6. A sixteen-celled family formed from four smaller families, 

 still connected at the corresponding angles, all the cells of like 

 figure and presenting the indication of continuous division. 



F. 7. Side view of a cell. 



F. 8. A four-celled family of peculiar form, which, perhaps, re- 

 presents a distinct species, of which, however, I [Prof. Reinsch] 

 have observed but a single specimen, the cell cruciate, formed of 

 four semicircular lobes, but whether the cells present the de- 



