THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 127 



SURIRELLA ANGUSTA KUETZ. 



Valve linear, with cuneate ends; otherwise as in S. pinnata. 

 Fresh water. 

 PL 36, Fig. 8. 



S. pinnata, S. panduriformis, and S. angusta have a narrow central area, and differ 

 from S. ovalis which has short costs;. 



SURIRELLA OBLONGA EHR. ? 



Valve elliptical-lanceolate, with obtuse ends; costas, marginal, 2 l /% in 10 ju; median 

 area granulate; pseudoraphe narrow, lanceolate, scarcely visible; striae about 18 in 10 ju- 

 L. 60 . 



Blue clay. Rare. 



PI. 35, Fig. 9. 



This has the outline and appearance of S. oblonga Ehr. (Mik. PL 15, Fig. 48), but the 

 costae are closer. 



SURIRELLA RECEDENS A. S. 



Valve ovate; costse, 2-2 }/2 in 10 n; pseudoraphe narrow, not reaching the ends of the 

 valve; intercostal spaces more evident near the middle. L. 50 ft. 

 Blue clay. Not uncommon. 

 PL 35, Fig. 7. 



SURIRELLA CRUCIATA A. S. 



Valve ovate; pseudoraphe very narrow; costse, 2 in 10 n; the outline of several of the 

 median costse strongly emphasized, while the other costse are indistinct. L. 54 ft. 

 Blue clay. 

 PL 35, Fig. 10. 



SURIRELLA GRACILIS GRUN. 



Valve linear, with sub-cuneate ends, slightly constricted in the middle; pseudoraphe 

 very narrow; costse, 6-7 in 10 n; transverse strise about 26 in 10 ft, punctate. L. 75 ft. 



According to De Toni (p. 598), this form is a Nitzschia. It has, however, a narrow 

 pseudoraphe. 



Pavonia, N. J., artesian well. Rare. 



PL 35, Fig. 11. 



SECTION 3 



SURIRELLA FASTUOSA EHR. 



Valve ovate; costse about 1-2 in 10 ft, dilated at the margin and contracting at about 

 one-fourth the distance toward the middle; area, ovate-lanceolate; pseudoraphe, narrow 

 and indistinct; intercostate strise more evident near the margin, 19 in 10 p., becoming again 

 evident in a narrow band about one-half the distance to the pseudoraphe. L. 50-120 ft. 

 Along the coast. More common southward. 

 PL 35, Fig. 1. 



9 



