4<D2 NITZSCH1A. 



var. debitis. (H.V.H. At!., pi. 69, f. 28 and 29*; Type No. 412), 

 plate 17, fig. 555. 



Valves somewhat narrower. 



Ard. Lieg, (De Wild.). England (H.V.H., Type No. 428). 



var. tenui rostris. (H.V.H. Atl, pi. 69, f. 31*), plate 17, fig. 556. 



Apices with narrow, rather long rostrum. 

 St. Josse ten Noode (Delogne). Ard. Liege. (De Wild.). 



var. fonticola Grun. (H.V.H. Atl., pi. 69, f. 15 and 20* ; in Type 

 No. 143), plate 17, fig. 557. 



Valves lanceolate, with rostrum well marked, 14 or 15 carinal dots and 

 28 to 30 striae in 1 c.d.m. Length, 1 to 3 c.d.m. Breadth of valves, 3*5 

 to 4/x. 



Fresh water. -Brussels (Delogne). 



N. microcephala Grun.! (Arct. Diat., p. 96; H.V.H. Atl., pi. 



69, f. 21*; in Type No. 12), plate 17, fig. 558. 



Very small ; valves lanceolate, linear, with apices rostrate-capitate; 12 to 

 13 carinal dots and 33 striae in 1 c.d.m. Length, 1 to 1*5 c.d.m. Breadth of 

 valves, about "3 c.d.m. 



Brackish water. Blankenberghe. 



var. elegantula. (H.V.H. Atl., pi. 69, f. 22^*), plate 17, fig. 559. 



Valves more regularly linear; 12 carinal dots and 26 striae in 1 c.d.m. 



Brackish water. Blankenberghe. 



N. communis Rabenh. (Alg., 949; Grun. Arct. Diat., p. 97; 

 H.V.H. Atl., pi. 69, f. 32*; Type No. 219), plate 17, fig. 560. 



Valves somewhat elongated, with apices abruptly tapering, not rostrate. 

 Carinal dots well marked, about 10 to 11 in 1 c.d.m. Length, 2*5 to 3^5 

 c.d.m. Breadth of valves, "5 c.d.m. ; breadth of girdle face, *8 c.d.m. 



Fresh water. Common. 



var. abbreviata Grun. (H.V.H. Atl., pi. 69, f. 35*; in Type No. 

 144), plate 17, fig. 561. 



Very small and rather broad, 12 to 14 carinal dots and 30 striae in 1 

 c.d.m. Length, - 6 to 1*3 c.d.m. Breadth, "25 to "3 c.d.m. 



Brackish water. On the piles of the Scheldt at Antwerp. 



var. obtusa Grun. (H.V.H. Atl., pi. 69, f. 33 and 34*), plate 17, 

 fig. 562. 



Valves lanceolate, with apices attenuate, subrostrate, truncate. 



Fresh water. 



