OP THE EUNOTIE^. 



759 



FxVMILY I.— EUNOTIE.^. 



Frustiiles free or adnate, in lateral \'iew lunate or arcuate, with transverse 

 striae or costoo, not interrupted by a central nodule or longitudinal line. The 

 essential characters of this group are the lunate form of the frustules in the 

 lateral \dew, and the stria? being continuous across the valve, and not inter- 

 rupted by a longitudinal line. It is easily distinguished, except from some 

 species of Synedi'a, which, however, are Hnear-ciurved rather than lunate, 

 and usually have an evident though faint longitudinal line. Ampliipleura 

 inflexa, which in form more nearly resembles Eimotia, has a longitudinal 

 line passing down the middle of the lateral valves. The Eunotieae have one 

 siuface of their connecting zone flat or concave and the opposite one convex, 

 the convexity being usually greater than the conca\ity. The lateral portions 

 or valves are either flat or convex ; in the former case they do not appear in 

 the front view, and the frustule appears quadi'ilateral ; in the latter, on a 

 front view, they have an oval form. Like most Diatomaceae, the connecting 

 zone has two puncta at each end. 



Genus EPITHEMIA (K.). — Frustules Innately curved in lateral view, and 

 furnished ^nth transverse internal ribs (canals, Sm.) ; usually adnate by the 

 flat or concave surface of the connecting zone, and not by one of the lateral 

 valves, like Cocconeis. The lateral view has strongly-marked transverse lines, 

 which Mr, Smith, in his beautiful work ' The British Diatomacese,' calls 

 canaliculi. We consider them internal ribs ; in fragments it is b}^ no means 

 difiicult to see them, as they give a dentate appearance to the margin ; their 

 form is somewhat triangular, but we are unable to detect any internal cavity 

 or canals. Mr. Smith, however, may have used microscopes of larger angular 

 aperture and higher magnifying powers than we employed. Besides these 

 ribs, the valves have transverse striae or punctated lines. The adnate fi^us- 

 tules and strongly-marked ribs distingiiish Epithemia from Eunotia and 

 Himantidium. In the front view the ends of the ribs frequently produce a 

 beautiful beaded appearance. These beads form two longitudinal lines, and 

 are more or less remote from the margins, according to the convexity of the 

 lateral valves. They are frequently more numerous on one side than on the 

 other, and are not all equidistant, even in the same series. 



* Front vieiv gihhous at the centre, 

 costcejine. 



Epithemia gibha (E.,K.). — Front \dew 

 elongated, linear, inflated at the centre 

 and ends. KB. p. 33, t. 4. f 22. = Na- 

 vicula gihba, E Inf. p. 184; Ennotia 

 gtbha, EA & M, many figm'es. Fresh 

 water, Coimnon. Ehrenberg gives about 

 100 habitats in Em^ope, Asia, Australia, 

 Africa, and America, (xii. 27.) Striss 36 

 in _ -001"; costae 15 in -OOl".— Distin- 

 guished by its elongated frustules, fine 

 striae, and dilated ends; but, from its 

 nearly straight side-view, its proper genus 

 may be overlooked. 



_ E. ventricosa (K.). — Front view ellip- 

 tic, oblong, with gibbous middle ; valves 

 arcuate, with gibbous dorsum and atte- 

 nuated, acute, somewhat incurved Puds ; 

 striae fine. KB. p. 35, t. 30. f 9 : SBD. 



i. pi. 1. f. 14. Fresh and brackish water. 

 Europe. 



E. cmgidata (Perty). — Dorsum turgid, 

 sloping to the obtuse ends ; venter con- 

 cave at the centre, striae about 12 in 

 1-1200". Rab Diat. p. 18, t. 1. f. 18. = 

 Eunotia Jastrahensis, EM. pi. 8. 1. f . 3 ? 

 Switzerland. Fossil. Hungary. Ac- 

 cording to the figures, the frustules 

 are gibbous or rhomboid in the front 

 view. 



2* Front view with marginal bead-like 

 dots formed hy the capitate ends of the 

 costcB ( = Cystopleura, Breb.). 

 E. Argus (E., K.). — Front view rect- 

 angular, with conspicuous ocelli tenni- 

 nating the stalk-like costae, and having 

 distinct strire interposed between them. 

 KB. p. 35, t. 20. f. 55. = Eunotia Argus, 

 EA. p. 125, & M. 1. 15 A, f. 59. Europe, 



