20 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



CYCLOTELLA MENEGHINIANA, VAR. STELLIGERA CL. AND GRUN. 



Differs from the type in the coarse radiating lines at the centre. 

 Broomall Lake, Media. 

 PI. 2, Fig. 4. 



CYCLOTELLA MENEGHINIANA, VAR. STELLULIFERA CL. AND GRUN. 



As in type but with the central rays granulate. 

 Broomall Lake, Media. 

 PL 2, Fig. 12. 



CYCLOTELLA STYLORUM (BR.?) V. H. 



Margin striated, the alternate striae thickened near the border, producing an appear- 

 ance of subquadrate cells. Centre faintly granulate, the outer border of which is encircled 

 by 10-12 puncta, each of which is surrounded by a small hyaline space. 



Blue clay. Rare. 



Van Heurck gives this form doubtfully as a variety of striata, while De Toni makes it 

 synonymous with it. Van Heurck's figure is not that of Brightwell, but as the specimen 

 above described is, I believe, exactly the same as Van Heurck's, I retain his name. 



PL 2, Fig. 10. 



CYCLOTELLA COMTA (EHR.) KTJETZ. 



Valve with marginal striae well marked, each third or fourth costa more robust than 

 the others. Central part finely striated, the striae punctate, radiating. 



Fresh water. 



PL 2, Fig. 7. 



The form here figured is probably the variety radiosa Grun. and is from a New Eng- 

 land specimen. It is quite likely to occur in this locality. 



CYCLOTELLA OPERCULATA (AG.) KUETZ. 



Frustules in zone view undulated. Angles rounded. Marginal costse alternating 

 with minute spines; centre nearly smooth, depressed, convex or flexuose. 



Fresh water. 



PL 2, Figs. 5 and 6. 



The figure is drawn from a specimen from Boston, Mass., H. L. Smith Type Slide No. 

 107, marked equivalent to C. minutula Wm. Sm. 



CYCLOTELLA ANTIQUA WM. SM. 



Marginal costse alternating with thick puncta; centre finely granulate with subtrian- 

 gular elevations. Frustules in zone view rectangular. 



Blue clay. 



PL 2, Fig. 11. 



The form corresponds to the original specimens of Wm. Smith in the deposit of Staven- 

 ger, Norway. 



The genus Cyclotella comprises about seventy specific names, many of which may be 

 referred to other genera, while some of Ehrenberg's are incapable of verification on account 

 of the small size of the figures and the lack of sufficient description. About half of the forms 

 are marine. The fresh-water species are usually found living in more or less stagnant water 

 or in pools contaminated with drainage, being an exception to the general rule that diatoms 

 are more abundant in water free from deleterious matter. 



