THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 109 



DlSTANTES 

 PINNULARIA LATA (BREB.) WM. SM. 



Valve linear-elliptical, broad; axial area broad, widened in the middle; striae slightly 

 radiate in the middle, 3 in 10 M; median line oblique, the terminal fissures hook-shaped. 

 L. 86 M. 



Blue clay. Not uncommon. 



PL 30, Fig. 23. 



PINNULARIA BOREALIS EHR. 



Valve linear, with rounded or sub-truncate ends; axial area about one-fourth the width 

 of the valve, widened in the middle; median line with large hook-shaped terminal fissures; 

 striae, 4 or 5 in 10 ^. L. 54 n- 



Blue clay. Occasional in fresh water in a smaller form. Specimens occur intermediate 

 between P. lata and P. borealis. 



PL 30, Fig. 22; PL 31, Fig. 12. 



PINNULARIA BOREALIS VAR. SCALARIS (EHR.) CL. 



Valve narrow, linear; axial area broad, widened into a transverse fascia; striae, 8 in 

 10 AI. L. 32 n- 

 Fresh water. 

 PL 30, Fig. 24. 



TABELLARI.E 

 PINNULARIA STOMATOPHORA (GRUN.) CL. 



Valve linear, with rounded ends; axial area less than one-third the width of the valve, 

 gradually widened in the middle to a transverse fascia; on each side of the central nodule is 

 a lunate space; striae divergent in the middle, convergent at the ends, 13 in 10 p; terminal 

 fissures very long, bayonet shaped. L. 75 /*. 



Cleve describes a variety continua as not interrupted. In some forms the fascia is 

 marked by very faint, short striae on the margin. 



Fresh water. Newtown Square. 



PL 30, Fig. 12. 



PINNULARIA GIBBA (KUETZ.) V. H. 



Valve linear, tapering to the subcapitate ends; axial area dilated in the middle; 

 striae, 10-11 M, divergent in the middle, convergent at the ends. L. 80 M- 

 Fresh water. 

 PL 30, Fig. 5. 



PINNULARIA MESOGONGYLA (EHR.) CL. 



Valve linear, gibbous in the middle, ends subcapitate; axial area narrow, widened in 

 the middle to a large orbicular space; striae strongly divergent in the middle, convergent 

 at the ends, 11 in 10 n. L. 60 ju. 



Fresh water. Common. 



PL 30, Fig. 6. 



