216 CYSTIPHOR.E. 



" So far as our acquaintance with these little Algee reaches, there appear 

 to exist four (if not five) distinct, yet kindred forms of figured ' Chroo- 

 coccaceae ' their remarkable shapes preclude their being regarded as 

 ' Lichen-gonidia,' but whether mature plants or stages in the growth of 

 any more complicated structure remains a problem. Ours are at least 

 forms which here and there recur, and one can at once recognise them as 

 always offering the same charactersitics and as maintaining their apparent 

 individuality. Whether they are ' species ' or not, it may be a matter 

 of convenience, should observers meet them elsewhere, and be able to 

 throw a light upon them, to have at least a means of their recognition ; 

 for these reasons it occurs to me as desirable to record them under 

 Reinsch's genus." W. Archer in Grevillea I., p. 44. 



Tetrapedia Crux -Michael! . Eeinsch Alg. Mitt. Frank. 



Cells quadrate, lateral margins entire, with two shallow con- 

 cavities, each extending half the length of the side, thus pro- 

 ducing an obtuse-angled central prominence, deeply incised at 

 the angles, incisions diagonal, 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 subacute (the incisions ultimately com- 

 pleted, and the cell breaking up ?) ; in side view lanceolate, 

 ends acute. 



SIZE. Cells -008--012 mm. diam. 



Archer in Grevillea i., p. 45. Eeinsch Algenflora, t. i., fig. 6. 



In running water (very scantily) near Mullingar, Co. West- 

 meath, Ireland. 



Plate LXXXVIL fg. 8. Cells magnified 600 diam. 



Tetrapedia Reinschiana. Archer in Grevillea I., p. 46, t. 3, f. 



11-13. 



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 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. 



SIZE. Largest cell 'OOTS-'Ol mm. diam. 



In moor pools, Co. Dublin and Wicklow. 

 Plate LXXXril. fig. 9. Cells magnified 600 diam. 



Tetrapedia setigera. Archer in Grevillea i.,p. 46, t. 3, fig. 14-17. 



Cells triangular, the lateral margins somewhat deeply ex- 

 cavated by a broad rounded sinus dividing the cell into three 



