150 ENCYONEMA. 



;i rather broad hyaline /.one, inflated round the central nodule, and extending 

 as far as the apex of the valve; stria- 7 or 8 in 1 cd.m, ; faint, finely divided 

 < ross wise, no! intermixed near the central nodule with shorter stria-. Length, 

 5 to 6 in 1 cd.m. 

 Fresh water, Not yet found in Belgium, Scotland (Gregory), West Ireland (West) 



; Hyaline zone not dilated round the central nodule. 



E. csespitosum Kutz. (Spec. Alg., p. 61 \ 11. v. II. Ail. Supp., 

 f. 3* ; Type No. 25), plate 1, fig. 46. 



Valve very broadly cymbi orm, with apices straight, obtuse, scarcely 

 constricted ; dorsal margin broadly convex, ventral margin regularly inflated ; 

 raphe almost straight, surrounded by a narrow hyaline /one, slightly inflated 

 in the middle; striae robust, divided crosswise, 10 to 12 in T cd.m. Length, 

 about 3 C.d.m. 



Fresh water. Here and there in sm.ill quantities, almost everywhere very variable, passes into 

 the t' illowing forms by all intermediate stages. 



Var. Auerswaldii. (E. Auenwaldi Rabh. I I.Y.I I. Atl., pi. 3, f. 14*), 

 plate 1, fig. 47- 

 Apices rounded, produced subrostrate. 



Var. lata. (II.Y II. Atl., pi. 3, I. 13*), plate 1, fig. 48. 

 Valve very widely lanceolate, sub elliptic ; apices very obtuse. 



E. ventricosum Kutz. (Bac, p. 80; H.V.H. Atl., pi. 3, f. 17*; 



Types Nos. 36, 37, 38), plate i, fig. 49. 



Valve cymbiform, somewhat elongated, apices often rather abruptly 

 attenuate; dorsal margin rounded, ventral margin straight, or almost straight ; 

 raphe straight, surrounded by a narrow hyaline zone, not inflated round the 

 central nodule ; stri;u faint, about 12 to 16 in 1 c.d.m. at the middle of the 

 valve, according to the size of the latter. Length, very variable, from 1-25 



to 2*5 c.d.m. 

 Fresh w ater.- Rather common. 



This species is excessively variable, not only in size, but also as to form ; 

 the apices are sometimes obtuse, in no way constricted, at other times rather 

 constricted longitudinally, at other times somewhat prolonged into points 

 beyond the ventral margin. Cleve unites this form with E. acspitosum. 



Sec. II. Valves very elongated, being 5-9 times longer than broad. 

 E. lunatum (W. Sm.) H.V.H. (Cymbella lunata IV. SmJ 



in Grev. Ann., 2nd ser., vol. 15, pi. 0, f. 5, H.V.H. Syn., pi. 3, f. 23*, Type 

 K- 39)> plate 28, fig. 791 bis. c. 



