112 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



EPITHEMIA ZEBRA VAR. PROBOSCIDEA (KUETZ.) GRUN. 



Valve convex on the dorsal, concave on the ventral side; costse, 3-4 in 10 jtc, slightly 

 radiating; apices recurved, capitate. 

 Blue clay. 

 PI. 31, Fig. 18. 



EPITHEMIA GIBBERULA VAR. PRODUCTA GRUN. 



Valve narrow, lunate, with produced and arcuate apices; costse radiate, 3-4 in 10 n ; 

 strise, 16-18 in 10 n, punctate. L. 58 M, usually smaller. 

 Blue clay. 

 PL 31, Fig. 19. 



EPITHEMIA MUSCULUS KUETZ. 



Valve short, strongly arcuate on the dorsal, concave on the ventral side; apices slightly 

 produced; costse radiate, about 5 in 10 n; striae, 15 in 10 n, punctate. L. 20-60 y.. 

 Shark River, N. J. 

 PL 31, Fig. 20. 



EPITHEMIA MUSCULUS VAR. CONSTRICTA (BREB.) V. H. 



Frustule elliptical, slightly constricted in the middle. Valve convex on the dorsal, 

 straight on the ventral side; costse about 4 in 10 M; striae about 18 in 10 p, finely punctate. 

 L. 45 M. 



Epithernia succinta Br6b. 



New Rochelle, N. Y. 



PL 31, Fig. 22. 



RHOPALODIA MUELLER 

 (Rhopalodes, like a war club) 



Frustule in zone view linear, linear-elliptical (in our species), or clavate. Valve reni- 

 form or lunate; a raphe, not visible in some species in the usual position of the valve, is 

 found along the convex edge or keel. Median and terminal nodules, although very small, 

 can be determined. The name is more appropriate to the African species which are clavate. 

 Two species only are found in this locality. 



The chief distinction between Epithemia and Rhopalodia is in the position of the raphe 

 and the nodules. In R. gibba and R. ventricosa the costse are parallel and not radiate 

 since the valves are not lunate. 



Chromatophore a single band irregularly divided. 



RHOPALODIA GIBBA (KUETZ.) MUELLER 



Valve linear, arcuate on the dorsal, straight on the ventral side, reflexed at the extrem- 

 ities. Costse, 6-7 in 10 M; strise about 14 in 10 M- L. 80-200 M- 



Fresh water. Common. 



PL 31, Fig. 23. 



In this species the raphe and nodules can be seen only when the valve is examined at 

 right angles to its usual position. 



