126 THE AMERICAN MONTHLY [July, 



b. Margins crenate, undulate, dentate or granulate (c). 



b. " not crenate, undulate, dentate nor granulate (<a^). 



c. Margin crenate (5) . 

 c. " undulate {t) . 

 c. " granulate (n) . 



c. " dentate or notched; end truncate, smooth ; sides toothed, convex. 



Reinschii^ 68. 



c. " " end 4-spinecl ; sides smooth, convex . aculeatum, 66. 



d. Cell twice or more longer than v^ide (/)• 



d. Cell i^ or less than tvs^ice longer than w^ide (^) . 



d. Cell less than i^ times longer than vv'ide (w). 



e. Margins crenate, undulate, dentate or granulate (z'). 

 e. Margins smooth ; basal angles not toothed (u') . 



e. " basal angles each with i tooth or papilla, 



Smolandicitm^ 69. 

 J~. VerrucEe or granules in patterns, or more or less restricted (x) . 

 y. *•' " not in patterns; more or less covering the sur- 



face (cc). 

 g". Spines on the whole surface; cell suborbicular ; sinus elliptical, 



aculeatum, 66. 

 g. Spines marginal, conical ; centre with 7 granules, and punctate, 



trachypleurtim^ 73. 

 k. Margins crenate, undulate, or dentate {/J)- 

 h. Margins smooth (//) . 

 /. Verrucae or gi-anules in patterns, or more or less restricted (nn) . 



"■ " not in patterns, more or less covering the surface (z^x') • 



J. End roimded ; semi-cell oblong, sides almost parallel . De I>aryi\ 58. 



J. '^ semi-cell spherical monilifornie., 60. 



j. "• semi-cell elliptical or oval . . cordamnn^* obloitgum.^ 



j . End truncate ; semi-cell quadrate, sides almost parallel . . anceps., 59- 



J. '• semi-cell pvramidal parvuhim, 59. 



k. Cells joined by pellucid bands into families ^tdmbyii., 6\. 



k. Cells not joined into families (/). 



/. Ends rounded ; semi-cells oblong cucti?nis., 58. 



/. " semi-cells oval ; diameter yy^YY in. (23//) . Witrockli.-\ 



I. Ends truncate ; semi-cells pyramidal, sides convex ; diameter -gi-^ to yyVj- 



(22-38,^.) notabile., -66 



I. Ends truncate ; semi-cells pyramidal, sides convex ; diameter -g^-jr to -^-^ 



(50-85//) pyratnidatuni., 69 



/. Ends truncate ; semi-cells pyramidal, sides convex ; diameter -^j}^^ to -^\j 



(35-43;/) pseu dopy ram I datum., 69 



/. Ends truncate ; semi-cells pvramidal ; sides straight or slightly concave 



grafiafznn., 60 

 7n. Cell conspicuously broader than long ; semi-cells subsemicircular ; side 



view circular, end view" elliptical scenedesmiis^ 59 



m. Cell \ to -I longer than broad (//) . 



n. Ends rounded ; semi-cell subcircular, sinus a mere notch, globostim. 60 



n. " semi-cell subsemicircular (<9). 



n. " semi-cell oval (;-). 



n. " semi-cell elliptical, or hexagonal-elliptical ; cell 1 longer 



than wide sexangulare. 63. 



n. Ends truncate ; semi-cell hexagonal ; diameter yjVo ^"- (^i/^-) oi' less, 



polygonum., 6^. 



* Journ. R.Micr.Soc, Dec, 1885. t Journ. R. Micr. Soc, Feb , 1886. 



