THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 83 



CALONEIS POWELLII (LEWIS) CL. 



Valve linear, with cuneate ends; axial area linear; central area large, quadrate, united 

 to the wide longitudinal lines; striae parallel, smooth, 8 in 10 ju. 

 Long Island (Lewis) ; Smith's Island, Delaware River. 

 PI. 21, Fig. 10. 



NEIDIUM PFITZER (is7i) 

 (neidion, dim. of naus, a boat) 



Valve linear or lanceolate; median fissures turned in opposite directions, terminal 

 fissures appearing bifurcate (?) ; striae transverse, usually oblique, finely punctate, crossed 

 by one or several longitudinal blank lines. 



Chromatophores, two, lying on the girdle side, in cell division each forming a partially 

 divided pair. A large pyrenoid is said to be found in the middle of each chromatophore, 

 but Mereschkowsky states that the pyrenoids are absent, but that in N. affine four elaeo- 

 plasts are always seen in the centre of the frustule. 



A genus easily recognized by the peculiar terminal and median fissures and by the 

 yellowish or brownish color of the valves when dry, darker than in Caloneis. 



NEIDIUM AFFINE (EHR.) PFITZER 



Valve linear, with protracted, sub-rostrate or capitate ends. 

 Navicula affinis Ehr. 



NEIDIUM AFFINE VAR. GENUINA FORMA MAXIMA CL. 



Striae, 14 in 10 ju, punctate, oblique in the middle, convergent at the ends; puncta, 15 

 in 10 . L. 238 M. 



Pensauken, N. J. (artesian well). 



PI. 21, Fig. 11. 



Var. genuina forma minor Cl. L. 26 /u; striae, 24 in 10 M- 



Brandywine Creek. 



PL 21, Fig. 12. 



NEIDIUM AFFINE VAR. AMPHIRHYNCUS (EHR.) CL. 



Valve linear, with protracted capitate ends; striae transverse, interrupted by several 

 longitudinal lines. 

 Willistown, Pa. 

 PL 21, Fig. 13. 



NEIDIUM AMPHIGOMPHUS (EHR.) PFITZER 



Valve with parallel margins and cuneate ends; striae transverse, interrupted by several 

 longitudinal lines; central area widened transversely. 

 Navicula amphigomphus Ehr. 

 Wissahickon. 

 PL 21, Fig. 14. 



NEIDIUM PRODUCTUM (WM. SM.) CL. 



Valve linear, elongate, with capitate apices; striae slightly oblique; longitudinal lines 

 marginal; axial area very narrow, central area small. 

 Navicula producta Wm. Sm. 

 Newtown Square. 

 PL 21, Fig. 16. 



