39 



NITZSCHIA. 



transversely elongated. Stride fine, about 17-5 to 19 in 1 c.d.m. Carinal 

 dots about 6-5 to 7 in 1 c.d.m. Girdle face very broad, constricted at the 

 median portion, with connecting zone finely plicate. Length, S to 15 c.d.m. 



Marine. Not yet found in Belgium, but found in England (W. Sm., Comber, Norman, Stolt. ). 

 Ireland (O'Meara), and throughout most of Europe. 



var. minor Grun. (H.V.H. All., pi. 60, f. 2 and 3*), plate 15, 

 fig- 5*3- 



Small (5 to 7 c.d.m. in length) with very fine striae (23 to 27 in 1 

 c.d.m. 



Marine. 



Group 9. Grunowia. 



Keel very eccentric, with dots elongated into costae, which 

 generally occupy a moiety of the valve. 



ANALYSIS OF SPECIES. 



J' Valves narrowly lanceolate, with margins not sinuouj ; costos diminishing 

 very gently in breadth . . . . . N. Denticula. 



Valve with margins sinuous or strongly inflated at the median portion ; 



costoe stopping abruptly in the middle of the valve . . N. sinuata. 



N. Denticula Grun. ! (Arct. Diat, p. 82 ; H.V.H. Atl., pi. 60, 

 f. 10*; Type No. 384), plate 15, fig. 514. 



Valves narrowly lanceolate, with apices acute or subacute, not rostrate, 

 furnished with costal which most frequently traverse the entire valve, while 

 diminishing very gently in breadth ; stria? fine, 15 to 18 in 1 c.d.m., distinctly 

 punctate; costs} 6 to 8 in 1 c.d.m. Length, 1*5 to 4^5 c.d.m. 



Fresh water. Throughout Europe. 



var. Delognei Grun. ! (H.V.H. Atl., pi. 60, f. 9*), plate 15, 

 fig- 5i5- 



Costse not reaching, at most, farther than to a moiety of the valve ; 

 striae very delicate, 24 or 25 in 1 c.d.m. Length, 1 to 2 c.d.m. 



Fresh water. Brussels Botanical Gardens (Delogne). 



N. sinuata (W. Sm.) Grun. ! (Arct. Diat., p. 82 ; H.V.H. Atl., 



pi. 60, f. n* ; Type No. 385), plate 15, fig. 516. 



Valve lanceolate, with margins triundulate, median portion inflated, apices 

 rostrate-capitate ; costae 5 or 6 in 1 c.d.m., only occupying a moiety of the 



