THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 117 



PANDURIFORMES 



NITZSCHIA PANDURIFORMIS GREG. 



Valve elliptical, constricted in the middle, with sub-cuneate apices; longitudinal fold, 

 with a punctate longitudinal line; striae transverse and oblique, 15 in 10 M; keel puncta, 6 

 in 10 p.. L. 108 n. 



Along the coast. More often found southward. 

 PL 39, Fig. 2. 



NITZSCHIA PANDURIFORMIS VAR. MINOR GRUN. 



Valve elliptical, constricted in the middle, with cuneate apices; keel puncta, 9 in 10 

 ju; striae in transverse and oblique lines about 20 in 10 n; longitudinal fold bordered by a 

 punctate line. L. 34 /*. 



Pavonia, N. J., artesian well. 



PL 32, Fig. 5. 



The var. continua Grun. is reported as occurring in Shark River. It varies in having 

 the longitudinal fold punctate. It is also usually smaller than var. minor. 



APICULATjE 

 NITZSCHIA APICULATA (GREG.) GRXJN. 



Valve oblong-linear, with cuneate-apiculate apices; striae punctate, apparently inter- 

 rupted or pervious, about 18 in 10 ju. L. 26 /*. 



Chester River, Md. 



PL 32, Fig. 6. 



The puncta are continued across the valve, but are less distinct on the fold. The 

 figure shows the entire frustule with the fold on each valve. The valves are sometimes 

 slightly constricted. 



NITZSCHTA ACUMINATA (WM. SM.) GRUN. 



Valve linear, sometimes slightly constricted in the middle, with acuminate apices; 

 longitudinal fold entirely without or with indistinct striae; keel puncta not evident; striae, 

 14-15 in 10 M. L. 82 M . 



Port Penn, Delaware River. 



PL 32, Fig. 13. 



NITZSCHIA PLANA WM. SM. 



Valve linear; apices acute, slightly constricted in the middle; longitudinal fold further 

 from the keel than the margin, broad, with scattered puncta; strise subtle, irregular, inter- 

 rupted, about 18 in 10 M! keel puncta oblong, 3-6 in 10 ju. L. 100-170 ju. 



Blue clay. Along the coast. 



PL 32 Fig. 2. 



