THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 101 



NAVICULA YARRENSIS GRUN. 



Valve elliptical-lanceolate, with rounded ends; axial area lanceolate, widened in the 

 middle; striae, 5 in 10 /u. L. 97 p.. 

 Cape May, N. J. Common. 

 PL 25, Fig. 14. 



Fig. 15, a smaller form, 65 p. in length; striae, 6 in 10 p.. 

 Fig. 16, 54 p. in length; striae, 8 in 10 p. (near var. valida Pant.). 



"Xii:- 



NAVICULA ELEGANS WM. SM. 



^^^ 



Valve elliptical-lanceolate, with produced ends; axial area very narrow, central area 

 large, orbicular; striae strongly divergent in the middle, slightly, if at all, convergent at the 

 ends, curved toward the margin, indistinctly lineate, 9 in 10 p.. L. 95 p,. 



Blue clay. Not rare. 



PL 31, Fig. 1. 



Navicula elegans var. cuspidata Cl. Valve as in type form but smaller and with 

 rostrate apices; striae, 10 in 10 ju- L- 82 ju. 



Belmar, N. J. 



PL 31, Fig. 2. 



Cleve remarks that the type form is acute and the striae 9, while the var. cuspidata 

 has 12 striae in 10 p.. In Fig. 1, PL 31, is represented a valve having 9 striae in 10 p., but not 

 acute, while Fig. 2, with but slight variation in striae, is more cuspidate. It is probable 

 there are intermediate variations. 



NAVICULA PALPEBRALIS BREB. 



Valve elliptical-lanceolate, with acute apiculate ends; axial area broad, lanceolate; 

 striae radiate, lineate, about 11 in 10 p.. L. 60 p.. 



Along the coast. 



PL 31, Figs. 6 and 7. 



On Plate 40, Fig. 5, is represented an abnormal form of Navicula in which the central 

 pores are in a line transverse to the longitudinal axis and each raphe is curved in a line 

 which almost returns to the centre. The puncta are in curved lines radiating from the 

 rounded hyaline centre. 



Pavonia, N. J., artesian well. 



Weissflog has described valves of Navicula somewhat similar in punctation. 



PINNULARIA EHR. (1843) 

 (pinnula, a small feather) 



Valve linear or nearly so, with rounded ends; axial area broad; central and terminal 

 areas large; costae smooth, transverse or radiating, usually convergent at the ends. 



The costae are channels on the inside of the valve, closed, except in the middle where 

 elliptical foramina, opening into the interior of the valve, give rise through their terminal 

 margins to the two longitudinal lines on each side of the valve. The raphe begins as a 

 groove in the side of the conical central nodule and continues as a cleft at right angles to 

 the plane of the surface of the valve, in which case the raphe forms a single line; if the raphe 

 is inclined to the valve surface, then two lines appear in projection, the upper and lower 

 edges of the cleft. In some forms the surface of the edge of the raphe on one side is folded 

 or grooved for a considerable distance, and the opposite edge is elevated into a ridge or 



