148 DESMIDS OF THE UNITED STATES. 



Var. tet:saceetjm, WoUe. Plate LV, figs. 1, 2. 

 Var. PEXTACEETJM, "Wollc. Plate LV, fig. 3. 



The one four-armed, and the other five-armed ; the crown 

 papillae correspond in number with the arms ; in other 

 details they are not unlike the typical form ; the serrate- 

 dentate margins vary greatly in different specimens. 



These varieties I collected only in Denmark Pond, Passaic 

 County, N. J., where they occurred frequently. 



St. macrocerum, Wolle. Plate LIV, figs. 3, 4, 5. 



Very large, granularly rough; semi -cells, front view, sub- 

 cuneate, truncate base and rounded top; upper angles later- 

 ally produced into long, slightly tapering, straight or lightly 

 incurved arms, margins serrate, ends bifid : end view six 

 radiate. Separated from the preceding partly by the less 

 number of arms, the less, central elevation (front view) and 

 the absence of the crown of papillae. 



Diameter 150-180 /<. 



Not rare in New Jersey waters. 



St. odontatum, Wolle. Plate LIV, figs. 8, 9. 



Of equal length and breadth; semi-cells in front view sub- 

 quadrangular, end convex, upper angles drawn out laterally 

 into straight or lightly incurved arms, as long as the breadth 

 of the body of the cell; margins serrate, apices furcate; the 

 lightly rounded inferior angles, each armed with a strong,, 

 short, aculeus. End view quadrangular, four rayed. 

 Diameter 62-75 yu. ; length 45 pL. 



Splitrock Pond, Passaic County, N. J. 



St. Eotula, JSTord. Plate LV, figs. 13, 14. 



Large, punctate, profoundly constricted ; semi-cells sub- 

 hexagonal, top truncate and furnished with a few teeth ; 

 angles produced laterally into long, straight rays, margins 

 with three (or four?) tooth-like prominences ; end view cir- 

 cular with seven to nine straight rays, margins tri-dentate- 

 crenate, apices trifid; at the base of each ray a large granule,, 

 area between, punctate. 



Diameter SS-125 //. Florida specimens 50-62 fx. 



Denmark, Splitrock, and other ponds, Passaic County, N. J. ;: 

 Florida. Very rare in Pennsylvania. 



St. coronulatum, Wolle. Plate LV, figs, il, 12. 



Twice as wide as long; semi-cells obovate; sides produced 

 into somewhat tapering, incurved arms, margins dentate; 



