50 NATURAL HISTORY SOCIETY OF DUBLIN. 



segments in front view very slightly longer than broad, sub-quadrate, 

 sides sometimes very slightly tapering, angles somewhat rounded, ends 

 rotundato-truncate, with a very gentle, often nearly imperceptible, mi- 

 nute central depression ; starch granule single, central ; in side view the 

 constriction acute within, widening outwards, segments somewhat 

 longer than broad, broadly elliptic, ends rounded ; end view broadly el- 

 liptic ; empty frond colourless, not punctate. Zygospore unknown. 



Measurements: — Length, g^; breadth, q-qqq', depth, -q-^-q of an 

 inch. 



PL I., Fig. 32, front view ; Fig. 33, side view. 



Affinities and Differences : — The oblong non-crenate figure and 

 smooth surface of this little form will readily distinguish it from every 

 every other at all agreeing with it in dimensions, such as Cosmarium 

 MenegMnii ; its size is, besides, in every way smaller than that of that 

 species. It is, indeed, amongst the largest species that a similarity of 

 figure is to be found ; and indeed, as far as concerns outward form alone, 

 it is difficult to define in a diagnosis the characters which separate this 

 little species from C. cucumis (Corda). In both the frond is oblong 

 and smooth, deeply constricted ; the segments subquadrate. But the 

 linear dimensions of this new form are some three or four times less 

 than those of the latter ; moreover, the former is sometimes more 

 than twice as long as broad — the latter is less than twice as long as 

 broad ; and, leaving the dimensions out of view, this character, appa- 

 rently slight, would help to an identification. But as concerns dimen- 

 sions, it would be as little necessary to compare Docidium minutum with 

 D. nodulosum or D. tnmcatum, or Euastrum elegans with E. ollongum 

 or E. crassum, or Closterium Cornu with C. acerosum, &c. This new 

 form differs, too, almost as greatly in size from Cosmarium quadratum 

 (Ealfs), and moreover wants the protuberance at each side near the base 

 of each segment present in that species. Thus, though the agreement 

 in figure of this new form with the species referred to is considerable, 

 I cannot fancy their being mistaken. But, moreover, the endochrome 

 in this new form has embedded in it in each segment but one central 

 large starch-granule. From C. cucurbita (Breb.) this form is quite dis- 

 tinguished by its deep linear constriction and non-punctate cell- wall, 

 besides dimensions and other special points at once recognisable by those 

 acquainted with these species; and, besides those mentioned, there are 

 none others with which it is in the least necessary to be contrasted. 



Genus — Penium (Br6b.) 



Penium Mooreanum (sp. nov.) 



Specific Characters : — Frond very minute, about one-third longer 

 than broad, sides somewhat barrel-shaped, ends truncato-rotund ; no 

 clear space with moving granules at the extremities ; zygospore qua- 

 drangular, oblong, compressed, angles mamillate, extremities nipple- 

 like. 



Locality : — Featherbed Bog, and near Lough Bray, conjugated. 



