NITZSCHIA. 401 



forma minor. (H.V.H. Atl., pi. 68, f. 3*; in Type No. 397), 

 plate 17, fig. 549. 



Only attaining 5-5 to 6 c.d.m. 



forma minima. (H.V.H. Atl., pi. 68, f. 4*), plate 17, fig. 550. 

 Still smaller, and scarcely 2 c.d.m. in length. 



var. incrustans. (H.V.H. Atl., pi. 68, f. 5 and 6*), plate 17, 

 fig- 55 1 - 



Valves more narrowly lanceolate, with 5 to 7 carinal dots in 1 c.d.m. Stria; 

 very fine, more than 30 in 1 c.d.m. Girdle face scarcely or not inflated at 

 the median portion. Length, about 2 to 5 c.d.m. Breadth of valves, -4 to -6 

 c.d.m. ; breadth of girdle face, up to nearly 2 c.d.m. 

 On piles in harbours. Ostond (Grun. !). Ilfracombe, England (Baxter Coll. No. 2627.) 



N. subtilis Grun.! (Arct. Diat., p. 95; H.V.H. Atl, pi. 68, 

 f. 7 and 8* ; in Types Nos. 165 and 190), plate 17, fig. 552. 



Valves narrowly lanceolate, very gently attenuate as far as the apices. Keel 

 with 7 to 10 dots in 1 c.d.m., the two median generally somewhat more 

 distant. Strioe fine, 30 to 32 in 1 c.d.m. Girdle face narrow, with apices 

 very slightly attenuate. Length, up to 9-5 c.d.m. Breadth of valve, about -5 

 c.d.m. ; and of girdle face, about 6 c.d.m. 



Fresh water. Rather common (?). 



var. paleacea Grun. (Arct. Diat., p. 95 ; H.V.H. Atl., pi. 68, f. 9 and 

 10*; in Type No. 10), plate 17, fig. 553. 



Smaller and narrower, valves attaining to 2^5 to 3*5 c.d.m. in length, 

 and "3 to '4 c.d.m. in breadth. Keel with 12 to T4 dots in 1 c.d.m. 

 Stria; very fine. 



Fresh and brackish water. Common (?) 



N. Palea (Kutz.) W. Sm. (S.B.D.,ii.,p.s 9 ;H.v.H.Ati.,pi. 6 9 ,f. 



22^ and 2 2<r* ; in Types Nos. 165, 196, 343 and 479 ; different varieties in 

 Types Nos. 411 and 413), plate 17, fig. 554. 



Differs from the preceding by the valves being more linear-lanceolate, 

 with apices shortly rostrate ; 10 to 12 carinal dots, the median not distant, 

 and ^3 to 3^ stria; in 1 c.d.m. Girdle face linear-lanceolate, with apices 

 rounded or truncate. Length, 2-5 to 6-5 c.d.m. Breadth of valves, about *5 

 c.d.m. 



Fresh water. Very common, 



CC 



