308 Transactions. — Botany. 



S. orbiculare, Ehrenberg. (E. XXI.) 



Common. 



8. muticum, Brebisson. (E. XXI.) 



Not uncommon. 



Differs from S. orbiculare in having a narrower isthmus between the 

 elliptic segments. 



8. polymorpMm, Brebisson. (E. XXII.) 



Common. 



S. gracile, Ealfs. (E. XXII.) 



Common. 



8. tetracerum, Kiitzing. (E. XXIII.) 



Eare. 



8. avicula, Brebisson. (E. XXIII.) 



Doubtful. Eare. 



Figures 31, 32. 



I have a specimen which seems to me to agree in all points with this 

 species, with the exception that the edges of the segments are slightly 

 crenated instead of smooth. The angles end in a forked spine or awn, 

 agreeing thus with 5. avicula. 



9. Didymocladon, Ealfs. 



D. Stella, sp. nov. 



Figures 9, 10. 



The frond is small; the segments in front view roughly fusiform, with 

 many long projecting processes ; two of these processes spring from each of 

 the opposite angles of each segment. Segments united by a rather wide 

 isthmus, so that the terminal separation is somewhat wide and gaping. Of 

 the two angular processes one in each segment is nearly parallel to the 

 corresponding one of the other segment ; the other is somewhat widely 

 divergent. Below these, at each end of the isthmus, spring two more 

 projections on each segment, pointing towards the other segment and 

 sHghtly outwards. Other processes spring from the outer portion of each 

 segment. All the processes have crenate edges, and each terminates in 

 three spines. The appearance of the frond in this view is like two roughly 

 fusiform bodies joined at the sides, and further clasped together by long 

 spiny branches projecting in all directions. 



The front view shows a star of many points. Focussed for the extreme 

 end, nearest the eye, it shows seven rays, behind which a number of others 

 are seen a little out of focus. As many of these rays are almost, if not quite, 

 in the same line as some in front or behind them, it is not easy to count the 

 exact number ; but I have made out as many as twenty-eight, and probably 

 that is the normal number. The rays (which are the processes seen in the 



