SPECIES OF DESMIDS. lOI 



^[ Lateral and basal lobes separated by a deep acute notch, 



Crux-Militensis, 1 1 1 



H" Lateral and basal lobes separated by a shallow rounded notch, 



speciosa.*^' 



I, Lobules deeply furcate; borders not serrate . . dichotoma, iii 



/. " not furcate, borders not serrate . . ringens, 112 



/. " " borders serrate . . serrulata.** 



in. End lobe remote from the lateral («). 



m. End lobe not remote from the lateral {0). 



n. End lobe triangular . . triangularis, 115 



n. " not triangular . . . . hamata, 114 



0. Lobes closely approximate, radiating (/ ). 



0. '■ " " not radiating, end lobe truncate, 



truncata, 114 

 /. End lobe triangular . . . . triangularis, 115 



/. " cuneate, end concave . .... conferta, 114 



/. " very broad, end truncate or convex . . crenata, 113 



r. Cytioderm papillose . . .... . apiculata, no 



r. " not papillose {s). 



s. Basal lobes with 4 subdivisions, lateral with 8; apices of end lobe 



furcate rotata, fimbriata, 109 



J-. " '' " " apices of end lobe 



not furcate . . . . . .... . cornuta. 



s. Basal lobes with 2 subdivisions, lateral with 4 (u). 



s. Basal and lateral lobes with the same number of subdivision (w). 



t. End lobe with i row of pearly granules .... Minnesotensis.\ 



t. " without pearly granules (_y). 



u. End lobe exserted on a long neck .... brachyptera, 1 10 



u. " exserted without long neck, its apices furcate, .f/OT//^*, no 



V. Margins spinous ... . brachypiera, no 



V. " not spinous bispinaia.\ 



y. Sinuses deep, inwardly widened and rounded; subdivisions of 



semi-cell 20-40; surface smooth radiosa, 109 



y. Sinuses deep, inwardly rounded, surface with rounded elevations, 



mamillafa.** 

 z. Lateral lobe deeply furcate, basal part perpendicular, furcations 



horizontal; ends bifid alata.** 



aa. A row of centrally larger basal inflations across each semi-cell, 



verrucosa.''''''^ 

 aa. No basal inflations; minutely granulate Jenneri, 115 



** F.-w Algae, p. 38 et seq. 



f Journ. R. Micr. Soc, Dec. 1885. 



