THE DIATOMACEJS OF PHILADELPHIA AND VICINITY 93 



the middle of the border, on each side, two striae approach each other closely with a short 

 stria between them; terminal fissures small, in the same direction. L. 120 n- 



Port Penn, Delaware River. 



PI. 24, Fig. 2. 



While variable in size and striation, approaching N. hennedyi, this species, as here 

 figured, is found in the Miocene and later deposits and is extant in most parts of the world. 



NAVICULA IRRORATA GREV. 



Valve oblong-elliptical, with cuneate-rostrate ends; striae, 7 or Sin 10 p., puncta, 7 in 

 10 p.; axial area bordered by puncta in unequal, transverse rows. L. 84 ju. 

 Blue clay. Rare. 

 PI. 24, Fig. 4. 



NAVICULA HENNEDYI WM. SM. 



Valve elliptical; areas semilanceolate; striae about 11 in 10 n, sometimes longer and 

 shorter on the margin; short rows of transverse striae along the axial area. 



Blue clay. 



PI. 25, Fig. 12. 



Var. circumsecta Grun. As in the type but with the lateral areas faintly striate or 

 punctate. 



Var. manca A. S. Valve lanceolate-elliptical, the lateral areas narrow and conver- 

 gent toward the ends; short rows of transverse striae along the axial area; striae, 9 in 10 /*; 

 central pores incrassate. 



Blue clay. 



PI. 25, Fig. 11. 



NAVICULA LYRA EHR. 



Valve elliptical, with rounded, sub-rostrate or sub-cuneate ends; lateral areas narrow; 

 striae, 6 to 14 in 10 M (Cl.), punctate. L. 50-180 /*. 



Var. ehrenbergii Cl. Lateral areas constricted in the middle, divergent at the ends. 

 Cleve refers to Schmidt, Atlas, PI. 2, Fig. 25, which is not divergent at the ends. 



Along the coast. 



PI. 25, Fig. 10. 



A narrower form occurs which has the areas divergent. 



Var. ? Valve elliptical, lateral areas narrow, convergent at the ends with short rows 

 of punctate striae; marginal striae, 10 in 10 n, punctate. L. 60 p.. 



Squan River, N. J. 



PI. 20, Fig. 5. 



Var. dilatata A. S. Valve elliptical, rostrate; lateral areas convergent in the middle 

 and nearly parallel or convergent at the ends. 



Blue clay. 



PI. 25, Fig. 13. 



N. lyra is exceedingly variable in outline, fineness of striation and in the lateral areas. 

 Intermediate forms occur approaching N. hennedyi and N. spectabilis. In N. hennedyi 

 the lateral areas are broad, semilanceolate, not narrowed in the middle. In N. spectabilis 

 the lateral areas are broad and narrowed in the middle. In N. lyra the lateral 

 areas are narrow and either constricted or not in the middle. In many forms in 



