142 CYMBELLA. 



Sect. i. Ventral and dorsal margins bent in contrary directions. 

 Valve broadly lanceolate or sub-elliptic. 



C. Ehrenbergii Kutz. (Bac. p. 79, pi. 6, f. n. h.v.h. Atl., 



pi. 2, f. 1, 2*; Type No. 15) ; plate i, fig. 22. 



Valves broadly elliptic-lanceolate, apices slightly produced rostrate ; raphe 

 a little bent, surrounded by a broad hyaline zone, rather enlarged near the 

 central nodule ; transverse striae about 8 in 1 c.d.m., robust and very finely 

 divided crosswise. Length 6 to 13 c.d.m. 



Fresh water. Common. 



C. cuspidata Kiitz. (Bac p. 79. pi. 3, f. 40; H.V.H. Atl, pi. 



2, f- 3* ; Type No. 16); plate 1, fig. 23. 



Valves broadly lanceolate, ventral margin sometimes depressed, with 

 apices longitudinally rostrate-cuspidate ; raphe bent, surrounded by a faint 

 hyaline zone, very inflated round the central nodule ; transverse striae 6 in i 

 c.d.m. in the middle of the valve, 12 in i c.d.m. at apices, finely divided 

 crosswise. Length 6 to 8 c.d.m. 



Fresh water.- Common. 



/3. naviculiformis Auersw. (in Rab. Alg, n. 1065; H.V.H. Atl., 

 pi. 2, f. 5*); plate 1, fig. 24. 



Considerably smaller, apices rostrate ; raphe straight ; hyaline zone 

 very inflated round the central nodule; striae finely punctate, about 15 

 in 1 c.d.m. ; length 3 to 4 c.d.m. 



Fresh water. Belgium, Ard. Liege. (De Wild.). Denmark (Heiberg). 



C. amphicephala Nsegeli (in Kiitz. Sp. Alg., p. 890; H.V.H. 



Atl., pi. 2, f. 6*; Type No. 19) ; plate 1, fig. 25. 



Valves elliptic with apices rostrate-capitate ; ventral margin sometimes 

 depressed ; raphe almost straight ; hyaline zone narrow, slightly inflated round 

 the central nodule, where the striae are also more distant; striae finely 

 punctate, about 12 to 14 in 1 c.d.m. Length 2^25 to 3 c.d.m. 



Fresh water. Antwerp, etc. (H.V.H.), Ard. Liege. (DeWild.) 



13. Anglica Lag. (Diat. Spitzb., p. 42, pi. 2, f. 18*), plate 25, fig. 

 695- 



Only differs from C. amphicephala in the hyaline space surrounding 

 the raphe. This hyaline space is more visible in the C. Anglica. 



Fresh water. Belgium, Ard. Liege. (De Wild.). England (W. Sm.). Spitzbergen 

 (Lagerstedt.) 



