DUBLIN NATUEAL HISTOKY SOCIETY, 81 



angustatum ; or which Docidnim EJirenlerghii does to D. nodulosum. In- 

 deed, I do not think there would be a possibility of confounding these 

 two Closteria if seen side by side. C. directum agrees with C. ohtusmn 

 (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 G. mnhhjo- 

 nenia (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 fr'ond. 

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

 tapering frond, but differs in the ends berag truncate, not rounded, and 

 the striae far more fine and close ; moreover, those species are conside- 

 rably more arcuate. G. directum differs from C.juncidum (Ealfs) 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 upAvards at the tapering 

 conical truncate ends ; endochrome with several fillets, and a single longi- 

 tudinal series of large granules ; empty frond very finely striate, reddish 

 near the ends. 



Locality: — -A pool at the top of Howth, conjugated; severals pools, 

 Dublin mountains. 



General Description : — Prond 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 

 depressed near the ends, owing to the upAvard inclination of the apices ; 

 endochrome bright green, reaching near the ends, and haviog beyond 

 it, close to the apices, the active granules — large granules in a single 

 series, longitudinal fillets several ; empty frond frequently slightly reddish, 

 especially near the ends — longitudinal striae very fine and very numerous, 

 in mounted specimens very difficult of detection, but in recent very 

 readily made out. Sporangium large, orbicular, or very broadly ellip- 

 tic, smooth, placed between the empty fronds, which are for some time 

 persistent. Conjugation taking place soon after self -division, one, the 

 younger, segment of each conjugating frond is much shorter than the 

 other, the older, longer segment, each of which lies in a parallel po- 

 sition, pointing in the same direction. 



_ It is with much gratification that I take the opportunity to name 

 this species after a well-knoAvn microscopist, — AndrcAV Pritchard, Esq., 

 author of several valuable additions to microscopical literature. When 

 at my request Mr. Pritchard did me the honour to permit me to dedicate 



