100 THE DIATOMACKE OF PHILADELPHIA AND VICINITY 



NAVICULA CUSPIDATA KUETZ. 



Valve rhombic-lanceolate, with acute ends; axial area linear, narrow, not widened in 

 the middle; strise transverse, 14-19 in 10 M (CL). L. 70-150 ju- 



Blue clay. Not uncommon in fresh water. 



PI. 26, Figs. 1 and 2. 



Fig. 2 represents an inner valve or stratum, with strong costse variable in size, formerly 

 known as Surirella craticula Ehr. 



N. cuspidata var. ambigua (Ehr.) Cl. Valve elliptical-lanceolate, with rostrate ends, 

 smaller than the type and with finer striae. 



Crum Creek. 



PI. 26, Fig. 3. 



NAVICULA SPICULA (HICKIE) CL. 



Valve narrow, lanceolate with acute ends; axial area narrow, central area dilated into 

 a stauros reaching the margin; transverse striae, 25-29 in 10 n, longitudinal closer. L. 

 50-130 (CL). 



Sometimes confused with N. crucigera. 



Stauroneis spicula Hickie. 



Newark, N. J. 



PI. 26, Fig. 4. 



NAVICULA CRUCIGERA (WM. SM.) CL. 



Valve lanceolate, narrow, with acute apices; central nodule a stauros reaching the 

 margin but crossed by two or three coarser strise; transverse strise, 12 in 10 n, punctate, the 

 puncta about 25 in 10 p. L. 80-100 /x (CL). Frustules in gelatinous tubes or free. 



Schizonema cmciger Wm. Sm. 



PL 26, Fig. 15. 



Reported as occurring in New York Bay, but I have not seen it. The figure is from a 

 specimen from another locality. 



MINUSCULE CL. 



Valve lanceolate or elliptical, chiefly distinguished by the small size; axial area indis- 

 tinct; central area small; striae radiate, very finely punctate. 



NAVICULA ATOMUS N^EGELI 



Valve elliptical, 6-8 M in length; strise radiate, 26-30 n, closer near the ends; axial 

 area linear, scarcely widened in the middle. 



Water-troughs and ditches. Probably common, but frequently not noticed because 

 of its minuteness. A mounting medium of the highest refractive index, such as realgar, is 

 required to resolve the striae. In the figure the strise are drawn a little coarser than they 

 appear in most specimens. 



PL 26, Fig. 12. 



CL. 



Valve lanceolate, axial area distinct; central area orbicular; striae coarse, indistinctly 

 punctate, approaching the costae of Pinnularia. 



