i30 THE AMERICAN MONTHLY July, 



yy. Cytioden-n verrucose ; end more or less protruding, not scolloped, 



ornatum^ 82 ; protr actum ^ 82. 



yy- " " end not protruding ; semi-cell twice as long as 



wide, oblong-quadrangular, angles rounded . . . Broomei, 86. 



zz. Cytioderm finely granulate or punctate ; semi-cells triangular, angles 



rounded, margins smooth Turpinii^ 158. 



zz. Cytioderm verrucose; semi-cell subreniform, 3 times as wide as long, 



commiszirale^ 83. 

 zz. "• " semi-cell pyramidal, angles rounded, 



tumiduni., 75. 



18. Tetmemorus. 



§ Cytioderm smooth or very indistinctly punctate (c). 

 § Cytioderm punctate (a). 



a. Cell 3 times as long as wide, irregularly granular ; base slightly plicate, 



giganteus., 92. 

 a. Cell more than 3 times as long as wide {b). 



h. Front and lateral views fusiform ; end with colorless, lip-like projection, 



granulatiis., 91. 

 /;. Front view cylindrical, not tapering; side view fusiform, tapering ; end 



rounded Brebissonii., 91. 



c. Three times longer than wide, smooth ; diameter y^'-g^^^ to yjV 0^ (18-20//) , 



ininutus^ 91 

 c. Four times longer than wide, smooth ; diameter ^i-^ (48/^'-) » linear 



elliptical, no lip penioides.* 



c. Four to six times longer than wide, smooth or indistinctly punctate ; 

 front view tapering, lateral fusiform, yo'-j, to yyg^ (20-22//.), 



lisvis., 91 . 



19. Xaxthidium. 



§ Spines divided at the ends armatum, 92. 



§ Spines subulate, ends not divided {a). 



a. Spines more or less scattered . . .• actileatnm^ 92. 



a. Spines marginal {b^ . 



b. Basal angles with 2 spines (</). 



b. " " I spine (c). 



c. Other spines geminate in 4 pairs cristatiim^ 93. 



c. "• " in 2 pairs on the end, single on the sides, 



asteptum. 93. 



d. Other spines 6 to 10 pairs on semi-cell ; protuberance beaded, 



biscna?-ii/}>t, 93. 

 d. Other spines 2 to 4 pairs (e). 



d. " none tetracoitrotiim., 95. 



e. Other spines, 4 pairs, terminal fasciculattim., 93. 



e. "■ 2 pairs, basal, vertical .... rectocorn7(ium, 94. 



e. " 2 pairs, terminal; a row of granules above the central pro- 



jection, a spine above the granules, .... Minneapoliense ^ 94. 



e. Other spines, 2 pairs, terminal ; a row of granules above the central pro- 

 jection, no spine above the granules polymaziiin. 94. 



e. Other spines, 2 pairs, terminal, no granules above the projection (y ) . 



f. Diameter yi„ in. (55-65//) or more fasciciilatum^ 93. 



f. "■ -5^ „^ in. (50//) or less ; semi-cell truncate-triangular, a;i-/e^/?^»^, 93. 



f. "• " " semi-cell not truncate-triangular, 



antilopcEZim., 94. 



*Journ. R. Micr. Soc, Feb., 1886. 



