52 THE DIATOMACEJE OF PHILADELPHIA AND VICINITY 



EUNOTIA PECTINALIS (KUETZ.) 



Valve linear, arcuate, apices slightly rostrate; striae distinctly punctate with puncta 

 in longitudinal rows nearer together at the ends. 



Himantidium pectinale Kuetz. 



Common in fresh water. 



PL 13, Figs. 6 and 7. 



The fasciae are associated in large masses, sometimes an inch or more hi diameter, and 

 late in August are found a foot or more in length, of a beautiful chocolate color. Exceed- 

 ingly abundant in the cedar-swamp streams of the Pine Barren regions of New Jersey. In 

 winter, the dead frustules form a parchment-like coating upon the twigs, dead leaves, and 

 other debris on the borders of streams. 



This species can scarcely be referred to Dillwyn's Conferva pectinalis, as, in his de- 

 scription, quoting Mueller, he says that "the filaments are of a dirty green color; seldom 

 exceeding half an inch in length." Dillwyn's form is probably Fragilaria virescens, which 

 equals Fragilaria pectinalis Ehr., while Kuetzing's species is Fragilaria pectinalis Ralfs. It 

 is not impossible to confuse Fragilaria virescens and Eunotia pectinalis when the zone only 

 is seen under a low power and their mode of growth is similar. 



EUNOTIA PECTINALIS VAR. UNDUIATA RALFS 



Valve as in type form, but with undulate margins. 

 Common in the cedar swamps of New Jersey. 

 PL 13, Figs. 8 and 10. 



EUNOTIA PECTINALIS VAR. SOLIEROLII (KUETZ.) 



Valve as in type, but with internal divisions as though in the process of reduplication. 

 Not common. Moorestown, N. J. (Palmer). 

 PL 13, Fig. 9. 



EUNOTIA PECTINALIS VAR. VENTRICOSA GRUN. 



As in type, but with the valves tumid in the middle. 



May's Landing, N. J. 



PL 13, Fig. 12. 



Fig. 11 is a form found in the blue clay. It differs in the coarser puncta from the var. 

 ventricosa. In outline it resembles Eunotia arcus Wm. Sm., which is Ceratoneis arcus 

 (Ehr.) Kuetz., but the central nodule is not present as in the latter form, which connects 

 Eunotia and Cymbella. It may be a form of E. luna Ehr. (A. S., Atlas, PL 286, Figs. 

 33 and 34.) 



EUNOTIA VENERIS KUETZ. 



Valve with convex dorsal and straight ventral margins, more or less constricted near 

 the sub-acute apices. Striae subtle, punctate. 

 Eunotia incisa Greg. 



May's Landing, N. J. Blue clay, Pavonia, N. J. 

 PL 13, Figs. 30 and 31. 



