118 THE DIATOMACE^E OF PHILADELPHIA AND VICINITY 



PSEUDO-TRYBLIONELLA 



NITZSCHIA LITORALJS VAR. DELAWARENSIS GRUN. 



Valve linear, with obtusely rounded cuneate ends, scarcely, if at all, constricted in the 

 middle; longitudinal fold wide; keel puncta, 5 or 6 in 10 n, sometimes confluent; striae ob- 

 scure, about 21 in 10 M- L. 75 /*. 

 Delaware River. 

 PI. 32, Fig. 12. 



This form is drawn from a slide of Christian Febiger containing an abundance of speci- 

 mens from Delaware City, and marked "Nitzschia dubia." 



CIRCUMSUTJS 



NITZSCHIA CIRCUMSUTA (BAIL.) GRUN. 



Valve elliptical, sometimes more than 200 n in length; longitudinal fold more or less 

 conspicuous; keel puncta about 4 in 10 n, the middle distant with the appearance of a 

 nodule; striae irregular, subtle, finely punctate, frequently interrupted. 

 Surirella circumsuta Bail. 

 Tryblionella scutellum Win. Sm. 

 Common in brackish water. 

 PL 32, Fig. 1. 



DUBLE 

 NITZSCHIA DUBIA WM. SM. 



Valve linear, scarcely, if at all, constricted in the middle, with cuneate, produced, 

 apiculate apices, somewhat recurved; keel very excentric; puncta sometimes partly pro- 

 longed, about 9 in 10 n; striae, 20-24 in 10 M- L. 93 p. 



Reported from along the New Jersey coast. I have not seen it. It is generally regarded 

 as fresh-water. Slides sometimes labelled N. dubia are in reality N. litoralis var. dela- 

 warensis. 



PL 39, Fig. 5. 



The figure is drawn from a specimen from another locality. 



BILOBAT^E 



NITZSCHIA BILOBATA WM. SM. 



Valve linear-lanceolate, constricted in the middle, apiculate at the ends; keel puncta 

 6 in 10 ju, prolonged unequally across part of the valve, the two median sub-remote; strise, 

 16 in 10 n. Frustule oblong, truncate, constricted in the middle. L. 120 p. 

 Shark River, N. J., Chester River, Md. 

 PL 32, Figs. 10 and 11. 



EPITHEMIOIDEjE 

 NITZSCHIA EPITHEMIOIDES GRUN. 



Valve linear, with cuneate, rostrate apices; slightly constricted on the keel side; keel 

 puncta, 8 or 9 in 10 //, extending as costae across the valve; striae delicate, 22 in 10 /*. 

 L. 47 /i. 



Brackish water, Long Island Sound. 



PL 32, Fig. 21. 



