THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 103 



The central nodule is scarcely evident, probably because it is not so thick as in other 

 forms. The outline is near to that of N. mesogongyla and certain forms of N. nobilis, 

 differing from the latter in the median line, striae and band which is wider than that of 

 P. latevittata var. domingensis Cl. 



Hammonton Pond, N. J. 



PI. 28, Fig. 2. 



A very beautiful form which I cannot find described or figured. It does not appear to 

 be N. major var. turgidula Cl., which has a narrow band. In the fossil deposit from Hop- 

 kinton, N. H., valves occur similar in outline but smaller. 



PINNULARIA NOBILIS EHR. 



Valve slightly gibbous in the middle and at the ends; median line complex; strise, 4 or 

 5 in 10 /i, slightly convergent or parallel at the ends, crossed by a band one-third as wide as 

 the length of the strise. L. ? to 350 ju. 



Blue clay. Fresh water. 



PL 28, Fig. 1. 



PINNULARIA DACTYLUS EHR. 



Valve broad, linear, slightly gibbous in the middle; ends broad, rounded; median line 

 not complex, sinuous; strise, 4 or 5 in 10 p., crossed by a very broad band. L. ? to 300 /* 

 Navicula gigas A. S. 

 Blue clay. Fresh water. 

 PL 28, Fig. 3. 

 Forms occur which are with difficulty assigned to either nobilis or dactylus. 



PINNULARIA DACTYLUS VAR. DARIANA (A. S.) CL. 



Valve linear-lanceolate, obtuse; axial area broad, less than one-third the width of the 

 valve; strise, 6 in 10 p, crossed by a broad band. L. 220 ju. 

 Absecon, N. J. 

 PL 29, Fig. 3. 



PINNULARIA DACTYLUS VAR. DEMERAR^E CL. 



Valve elliptical-lanceolate, with sub-cuneate ends; axial area lanceolate, broad in the 

 middle; median line flexuose; strise radiate throughout, 6 in 10 ^- L- 150 ju. 

 Blue clay. 

 PL 29, Fig. 10. 



PINNULARIA GENTILIS (DONK.) CL. 



Valve linear, with rounded ends; axial area about one-fourth the diameter of the 

 valve; strise radiate in the middle, convergent at the ends, 7 in 10 /*, crossed by a broad 

 indistinct band. 



Fresh water. Not common. 



PL 29, Fig. 1. 



PINNULARIA TRIGONOCEPHALA CL. 



Valve linear, gibbous in the middle and at the cuneate ends; axial area wider between 

 the middle and the ends, dilated to an elliptical space in the middle; strise, 6 in 10 p. 

 L. 145 M. 



Blue clay. 



PL 29, Fig. 8. 



