NITZSCHIA. 387 



Group. 3. Apiculat.k. 



Valves longly linear or somewhat attenuate at the median portion, 

 showing a sulcus on which the stria; are absent, or are less marked 

 than on the remainder of the valve. Keel very approximate to one 

 of the margins. 



ANALYSIS OF SPECIES. 



f Keel with very j Valve very large ; sulcus broad N - P lana 



distinct dots. ) ,, , , ,. , . 



\ V alve narrowly linear ; sulcus narrow . . . N. Hungarica. 



I Keel with indistinct (Sulcus very broad ; valve of medium size, robust . N. acuminata. 

 i. (.Sulcus veiy narrow ; valve small, very narrow . N. apiculata. 



N. plana, W. Sm. (S.B.D., I, p. 42, pi. 15, f. 114; H.v.H. Atl., 

 pl. 58, f. 10, 11*; Type No. 37S), plate 15, fig. 503. 



Valve longly linear, attenuate at the median portion, with cuneate apices, 

 broad well-marked sulcus, generally attenuate at the median portion, somewhat 

 more distant from the carina! margin than the other margin ; striae fine, about 

 18 in 1 c.d.m., constantly replaced in the sulcus by very irregular puncta. 

 Carinal dots very distinct, square or elongated, 3^5 to 6 in 1 c.d.m. Length, 

 attaining to 17 c.d.m. 



Brackish water. Not yet found in Belgium. England (W, Sm. ! Comber, Norman, Stolt. ). 

 Ireland (O'Meara). 



N. Hungarica Grun. ! (Arct. Diat., p. 73 ; h.v.h. Atl., pi. 58, 



f. 19-22*; Type No. 3S0), plate 15, fig. 504. 



Valve narrowly linear ; generally feebly constricted in the middle ; apices 

 cuneate, rostrate; sulcus narrow 7 , very distinct; striae fine, 16 to 18 in 1 c.d.m., 

 very delicate in the sulcus; carinal dots very distinct, 9 or 10 in 1 c.d.m. 

 Length, 5 to 1 1 c.d.m. 



Brackish, sometimes fresh water. Antwerp, Schaerbeeck (Delogne). Ireland (O'Meara). 

 England (H.V.H. Types, Nos. 7, 174, 186, 234, 389, 431,471). 



N. apiculata (Greg.), Grun. ! (Arct. Diat., p. 73; h.v.h. Atl, 



pl. 58, f. 26 and 27*; in Types Nos. 7, 12, 44, etc.), plate 15, fig. 505. 



Differs from the preceding species by its valves being generally smaller 

 and narrower, and by the carinal dots being absent or indistinct. Striae about 

 16 or 17 in 1 c.d.m. Length, 2-5 to 5 c.d.m. Breadth of valves, less than 

 1 c.d.m. 



Brackish water. Antwerp. England. Scotland. Finmark. Ireland (O'Meara). 



