NAVICULA. l8l 



Valve lanceolate, elongate, with apices rostrate, slightly capitate. Central 

 nodule surrounded by a rounded hyaline area. Striae rather robust, with very 

 feeble transverse divisions, radiant at the median portion of the valve, scarcely 

 convergent at the apices, about 16 in i c.d.m. Length, 2*5 to 3*5 c.d.m. 

 Breadth, about 0*5 c.d.m. 



Fresh and brackish water. Antwerp (H.V.H.), Ard. Lit5g. (DeWild.). Throughout Europe. 



var. veneta. (Nav. veneta Killz. ! H.V.H. At]., pi. 8, f. 3 and 4*), 

 plate 3, fig. 123. 



Smaller than the type form, with apices scarcely rostrate-capitate, stria? 

 distant, about 14 in 1 c.d.m. Length, about 2-5 c.d.m. Breadth, about 

 o'5 c.d.m. 



var. exilis. (H.V.H. Atl., pi. 8, f. 2*; Type No. 93), plate 3, 

 fig. 124. 

 Very short; rostrum scarcely marked. 

 Fresh water. Brussels. England. 



Constitutes the link with the following species. 



* * Apices extremely rostrate or rostrate-capitate. 



N. rhynchocephala Kutz. (H.V.H. Atl, pi. 7, f. 31*. 

 Type No. 90), plate 3, fig. 119. 



Valve broadly lanceolate, with apices strongly acuminate-capitate. Central 

 nodule surrounded by a rounded hyaline area. Striae robust, clearly 

 divided transversely, very slightly shortened round the central nodule. 

 The median ones radiant, the terminal feebly convergent, about 9 to 12 in 

 1 c.d.m. Length, about 5 to 6 c.d.m. 



Brackish water. Antwerp. Found throughout Europe. 



var. amphiceros. (H.V.H. Atl., pi. 7, f. 30*), plate 3, fig. 120. 

 More shortly lanceolate with apices strongly rostrate, feebly capitate. 

 Striae 8 to 10 in 1 c.d.m. 



Brackish wattr. Antwerp. 



var. rostellata. (iV. rostellaia Killz. ? H.V.H. Atl., pi. 7, f. 23 and 

 24*. Type No. 87), plate 3, fig. 121. 



Broadly lanceolate ; apices narrowly rostrate ; hyaline area surrounding 

 the narrow central nodule. Striae rather robust, about ic or n in 1 

 c.d.m. Length 4 to 6 c.d.m. 



Brackish water. Antwerp. Norfolk, England. 



N. gregaria Donkin. (Q.J.M.S., i86r, p. 10, pi. 1, f. 10*; 



N. cryptocephala IV. Sm. ; H.V.H. Atl., pi. 8, f. 12, 13, 14 and 15; 

 Type No. 94), plate 3, fig. 125. 



