62 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



Staurastrum Meyen. The second largest genus of 

 Desmids. Cells in front view oblong, cylindrical, elliptical, or 

 orbicular, with margins notched or smooth, always constricted 

 in the middle, ends rounded, entire. End view with three to 

 six obtuse, acute, or horn-like angles. Chlorophyll more or less 

 central, zygospores commonly furnished with spines (see 

 Fig. 261). 



S. orbicular e (Ehrb.) Ralfs, Figs. 123, 124. 



S. dejectum (Breb.) var. convergens Wolle, Fig. 122. 



S. dejectum var. mucronatum Ralfs, Fig. 125. 



6\ megacanthum Lund., Figs. 126, 127. 



5". hirsutum (Ehrb.) Breb., Figs. 133, 263, 263a. 



5\ brevispinum Breb., Fig. 128. 



S. leptocladum Nord., Figs. 264, 264a. 



S. erasum Breb., Figs. 130, 131. 



S. arctiscon Ehrb., Figs. 268, 268a. 



S. odonatum Wolle, Fig. 132. 



5. coronulatum Wolle, Figs. 267, 267a. 



5*. Ravenelii Wood, Figs. 134, 135. 



S. dejectum Breb., Figs. 233, 236. 



S. furcigerum Breb., Fig. 136. 



5. crenulatum (Delp ) Nag., Fig. 231. 



5. margaritaceum Ehrb., Fig. 235. 



5\ iotanum Wolle, Fig. 143. 



5". eustephanum Ralfs, Fig. 144. 



S. pygmceum Breb., Fig. 261. Conjugating. 



S. muricatum Breb., Fig. 129. 



Four* species, names unknown, Figs. 137-142. 



S. gracile Ralfs, found but not figured. 



Euastrum Ehrb. Cells elliptical or oblong, deeply con- 

 stricted ; semi-cells usually cut at the ends and wavy or lobed 

 at the sides, the number of lobes being uneven; usually 

 furnished with circular inflated protuberances. 



E. integrum Wolle, Fig. 105. 



E. verrucosum _ (Ehrb.) Ralfs, Fig. 104. 



E. oblongatum (Grev.) Ralfs, Fig. 229. 



E. ampullaceum Ralfs, Fig. 230. 



E. elegans Kiitz., Fig. 232. 



E. Nordstedtianum Wolle, Fig. 234. 



