210 BRITISH DESMIDIE.E. 



" Corpuscules chevelus, verts, presque a six lobes. Lobe du milieu trian- 

 gulaire, les coins exterieurs a deux pointes ; au milieu, deux cylindres vert 

 fonce, appuyes I'un centre I'autre. Chaque lobe lateral a trois decoupures, 

 et chaque decoupure a deux dents." 



16. M. foliacea (Bailey); frond subquadrate ; end lobes narrow, 

 with emarginate angles ; lateral lobes inciso-dentate, with a short 

 rounded tooth-like projection next the end lobe. 



Micrasterias foliacea, Bailey, in lit. cum icone (1847). 

 "Worden's Pond, Rhode Island, Bailey. 



" Frond small, smooth, nearly quadrangular in the general outline : seg- 

 ments composed of three principal lobes, of which the middle one is nearly 

 simple and emarginate : the lateral lobes are incised, in much the same 

 manner as in Micrasterias rotata, and all their subdivisions extend to an 

 equal distance from the middle line of the frond." — Bailey, in lit. 



Tab. XXXV. fig. 3. Frond di\dding, from a drawing by Professor Bailey. 



17. M. Turreyi (Bailey); frond orbicular; lateral lobes deeply in- 

 cised; inner subdivisions acute, external bidentate at the apex, all 

 tapering. 



Micrasterias Torreyi, Bailey, in lit. cum icone (1847). 

 Near Princeton, New Jersey, Bailey. 



This species connects the elliptic with the orbicular species. The end lobe 

 is narrow and not exserted ; the angles taper into acute points or spines. All 

 the incisions are deep. The lateral lobes have five subdivisions, two belonging 

 to the basal lobe and three to the intermediate ; but the distinction is obscure, 

 and only indicated by the rather deeper incision which parts them. Of the 

 subdivisions, that next the other segment and that adjacent to the end lobe 

 are bidentate at the apex, the rest taper gradually into acute points. 



Tab. XXXV. fig. 5. Frond from a drawing by Professor Bailey. 



1 8. M. muricata (Bailey) ; " segments divided by deep indentations 

 into three transverse portions ; the basal with three linear processes 

 on each side, the others with two on each side." 



Euastrum muricatum, Bailey, American Journal of Science and Arts, 1846, 

 p. 126. figs. 1, 2. 



Catskill Mountains, United States, Bailey. 



Micrasterias muricata belongs to the same section as M.furcata, but 

 differs from that and every other known species in some remarkable par- 

 ticulars. The division into five lobes is indicated merely by the presence of 

 processes, which, unlike those in the other species, do not diverge in the front 

 view, but spread laterally, in such a manner that the one nearest the eye 

 more or less conceals its companions. 



