250 AllCIIEll,, ON A NEW SPECIES OF COSMARIUM. 



nrc parallel or nearly so — in tlie latter the lower margin is 

 frequently curved upwards at the end^ and the upper margin 

 is convex ; and in the former the empty frond is far more 

 finely striate than in the latter^ while it is more nearly colour- 

 less. C. directum is a more slender, more linear, more bacillar 

 form than C. didymotocum, and, so far as comparative out- 

 ward form merely and length and breadth are concerned, may 

 be said to bear a relationship to that species somewhat similar 

 to that which Colsterium juncidum does to C. angustatum, or 

 which Docidium Ehrenberghii does to D. nodulosum. Indeed, 

 I do not think there would be a possibility of confounding 

 these two Closteria if seen side by side. C. directum agrees 

 with C. obtusum, Breb., in its scarcely tapering frond, but it 

 differs from that species in its truncate, not rounded, ends, as 

 well as in its striate, not smooth, empty frond. The latter, 

 indeed, appears to me more to resemble a somewhat slightly 

 curved Penium (so to speak) than a Closterium, as, indeed, 

 M. de Brebisson himself remarks, nor does he refer to moving 

 granules at the extremities. C. directum agrees also with C. 

 amblyonema, Ehr., in its scarcely tapering frond; but the 

 former differs from the latter in its smaller size, in its 

 straighter outline, in its truncate, not broadly rounded, ends, 

 and in its striate, not smooth, empty frond. C. directum 

 agrees with C. intermedium and C. angustatum in its scarcely 

 tapering frond, but differs in the ends being truncate, not 

 rounded, and the striae far more fine and close; moreover, 

 those species are considerably more arcuate. C. directum 

 differs from C. juncidum, Balfs, and C. gracile, Breb., by its 

 straight frond, not curved downwards at the ends, and by 

 its much less slender fronds. 



Closterium Pritchardianum, sp. nov. 



Specific characters. — Frond gradually tapering, curvature 

 slight ; lower margin very slightly concave, inclined upwards 

 at the tapering, conical, truncate ends; endoehrome with 

 several fillets, and a single longitudinal series of large gra- 

 nules ; empty frond very finely striate, reddish near the ends. 



Locality. — A pool at the top of HoAvth, conjugated; 

 several pools, Dublin mountains. 



General description. — Frond from about ten to fourteen 

 times longer than broad, somewhat stout, slightly curved, 

 tapering very gradually from the centre, towards the ends 

 more rapidly ; lower margin slightly concave, and inclined 

 upwards near the conically attenuated, truncate, reddish ends; 

 upper margin gradually convex, sometimes very slightly de- 



