THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 51 



EUNOTIA EHR. (1837) em. GRTJN. (1862) 

 (eu, well, and noton, a back, referring to the strong, ridged dorsum) 



Frustules free, in fasciae or epiphytic. Valve arcuate, without costse, transversely 

 striated; pseudoraphe absent; pseudo-nodules at each end. 



Chromatophores laminate along the concave zone and the valves. 



Very many species of Eunotia have been created to differentiate size and number of 

 crense or undulations. An examination of certain fossil deposits of New England, as well 

 as a gathering from the blue clay of Philadelphia, will show forms which vary infinitely. 

 E. major and E. gracilis are scarcely distinguishable because of the intermediate variations. 

 The strise in all forms are punctate, but the puncta are frequently confluent. 



ANALYSIS OF SPECIES 



Eunotia is divided into two sections, Himantidium and Eunotia proper. In Himan- 

 tidium, the frustules are in fasciae, either short or long. Among those with short fasciae are 

 major, gracilis, and nymanniana; those with long fasciae are pectinalis, solierolii and veneris. 

 Eunotia proper includes frustules, free or epiphytic, in which the valves are not dentate on 

 the dorsal margin, such as lunaris, hemicyclus, biceps and prserupta; and those in which 

 the valves are dentate or crenate on the dorsum, such as monodon, triodon, diadema and 

 others. 



The resemblance between Eunotia and Epithemia is noticeable. In both, the epiphytic 

 character of the valve is seen in the shape of the frustule which is arched, and, in the free 

 forms, is adherent at the ends only. In Epithemia, the median is more evident than the 

 terminal nodules. In Eunotia, there is no median nodule, but the end nodules, in some 

 species, are quite evident, and a tendency is shown to produce a very short raphe. The 

 arrangement of puncta in valve view is similar in both genera. 



SECTION 1. HIMANTIDIUM 

 EUNOTIA MAJOR (WM. SM.) RAB. 



Valve arcuate, linear, subcapitate, recurved. Striae punctate, 12 in 10 /* L. 90-190 ju. 

 Common in fresh water. 

 PI. 13, Figs. 1 and 2. 



EUNOTIA GRACILIS (EHR.) RAB. 



Valve with sides parallel; apices slightly capitate and revolute; strise, 10 in 10 p.. The 

 striae on the connective membrane more delicate than in E. major. Intermediate forms 

 occur. 



Common in fresh water. 



PI. 13, Fig. 3. Fig. 4 is indeterminate. 



EUNOTIA NYMANNIANA GRUN. 



Valve small, curved, with parallel dorsal and ventral margins; apices truncate and 

 recurved into dorsal elevations; striae delicate. 

 Blue clay. Not common. 

 PI. 13, Fig. 32. 



