THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 99 



uous; central area orbicular; terminal fissures small, hook-shaped; strise robust, 7 or 8 in 

 the middle, closer at the ends, indistinctly punctate or lineolate. 



Blue clay. Not common. 



PL 26, Fig. 11. 



Cleve states that this form belongs to the post-glacial deposits and is found living only 

 in the Hartz Mountains. 



NAVICULA INTEGRA WM. SM. 



Valve lanceolate with triundulate margins and rostrate-apiculate ends; strise radiate, 

 more distant in the middle, 20-23 in n, punctate; axial area very narrow, central area 

 rounded or elliptical. L. 33^13 /*. 



Pavonia, N. J., artesian well. Common in Chester River, Md. 



PL 26, Fig. 5. 



MICROSTIGMATIC.E CL. 



Valve lanceolate; axial area narrow; central area small, rounded; striae finely punctate, 

 nearly parallel. (Includes here only the division Libellus.) 



NAVICULA TUMIDA (fiREB.) CL. 



Valve lanceolate, with rounded ends; axial area narrow, central area elliptical; raphe 

 slightly sigmoid; striae, 13 in 10 n, finely punctate, a few shorter in the middle. 

 Scoliopleura tumida (Bre"b.) V. H. 

 Cape May, N. J. 

 PI. 25, Fig. 1. 



NAVICULA GREVILLEI (AG.) CL. 



Frustules in gelatinous tubes, rectangular; zone with numerous longitudinal divisions. 

 Valve elliptical-lanceolate, obtuse; axial area narrow, central area small; striae lineate, 

 about 18 in 10 ju in the middle where they are slightly radiate and more evident, closer 

 near the ends and transverse; median line with terminal pores distant from the ends. 

 L. 60 M. 



Schizonema grevillei Ag. 



East River, N. Y. 



PL 31, Figs. 3 and 4. 



NAVICULA LIBELLUS GREG. 



Valve rhombic-elliptical, obtuse at the ends; axial area narrow, central rounded, 

 small; strise punctate, slightly radiate, about 19 in 10 n; terminal fissures close to the ends, 

 indistinct. L. 60 M- 



Cleve describes this form as having acute ends, while Gregory states that it is "more 

 obtuse and broader than N. rhombica." Gregory's Figure 101 apparently shows the ends 

 acute, but he says that the valve view is "rhombic or elliptic-lanceolate, broad, with ob- 

 tuse ends" (Diat. of the Clyde, p. 57, PL 6). 



Hackensack Swamp, N. J. 



PL 31, Fig. 5. 



ORTHOSTICH^E CL. 



Valve lanceolate or elongated; axial area narrow; central area sometimes apparently 

 dilated into a stauros; stria? punctate, the puncta in transverse and longitudinal rows. 



