148 DESMIDS OF THE UNITED STATES. 



Var. TETRACERUM, Wolle. Plate LV, figs. 1, 2. 



Var. PENTACERUM, Wolle. 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 ju. 



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 j*. ; length 45 /*. 



Splitrock Pond, Passaic County, N. J. 



ST. EOTULA, Nord. 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 88-125 //. Florida specimens 50-02 //. 



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

 Florida. Very rare in Pennsylvania. 



ST. COROXULATUM, Wolle. Plate LV, figs. 11, 12. 



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

 into somewhat tapering, incurved arms, margins dentate; 



