78 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



FRUSTULIA INTERPOSITA (LEWIS) DE TONI 



Valve linear-elliptical, rounded at the ends; terminal nodules short. 



Navicula interposita Lewis. 



Along the coast. Port Penn, Delaware River. 



PI. 17, Fig. 5. 



AMPHIPLEURA KUETZ. (1844) 



(amphi, on both sides, pleura, a side) 



Frustules free, in gelatinous masses or in tubes. Valve linear-lanceolate; central 

 nodule narrow, extending half the length of the valve or more, then forking toward the ends. 

 Terminal nodules prolonged, as in Frustulia, into a " porte-cray on-shaped" figure. 



Chromatophores two, very short. 



AMPHIPLEURA PELLUCIDA KUETZ. 



Frustules free or in mucous masses. Valve fusiform; forks about one-fourth the length 

 of the valve; striae transverse, punctate, 36^40 in 10 /* (J. J. Woodward). 

 Occasional in the Delaware River. 

 PI. 17, Fig. 9. 



AMPHIPLEURA RUTILANS (TRENTEPOHL) CL. 



Frustules enclosed in gelatinous tubes. Valve linear-lanceolate, obtuse at the ends; 

 forks about one-third the length of the valve; striae, 28 in 10 n. 

 Conferva rutilans Trentepohl. 

 Schizonema dillwynii Wm. Sm. 

 Abundant at Belmar, N. J. 

 PI. 17, Fig. 10. 

 Fig. 11 represents a portion of the gelatinous tube containing frustules. 



DICTYONEIS CLEVE (1890) 

 (dictyon, a net) 



Frustules oblong. Valve lanceolate, constricted in the middle (in our species); an 

 outer layer finely punctate and an inner layer of reticulations; the margin of the valve 

 divided into large, quadrate cells. 



The genus Dictyoneis includes species at one tune ascribed to Mastogloia and Navic- 

 ula. The structure, however, is not like that of either, as the loculi are attached to the 

 valve and are not separable as in Mastogloia, and the cell-wall is not like that of any 

 Navicula. 



Cleve remarks that Dictyoneis is found in warm waters. Lewis found one specimen 

 at Black Rock Harbor, L. I., and one in the Delaware River blue clay. The specimens 

 here described I found living on the New Jersey coast. 



DICTYONEIS MARGINATA VAR. TYPICA CLEVE 



Valve panduriform, with cuneate lobes; axial area narrow, linear, scarcely, or not at 

 all, widened in the middle; terminal fissures in contrary directions; outer stratum finely 

 punctate, about 25 in 10 /*, in parallel striae; inner stratum coarsely reticulated. Four and 

 one-fourth times longer than broad; marginal cells, 5 in 10 ju, smaller or obsolescent in the 

 middle of the valve; cells of the valve in irregular transverse rows, 10-12 in 10 n. L. 93 /n. 



Navicula marginata Lewis. 



Absecon, N. J. 



PI. 20, Fig. 3. 



