NAVICULA. 179 



var. leptocephala Breb. (H.V.H. Atl., pi. 7, f. 16*; Type No. 84), 

 plate 3, fig. 107. 



Like the preceding variety, but still somewhat smaller. Valve with 

 median portion somewhat inflated, with apices gently tapering sub- 

 rostrate. 



Austruweel near Antwerp (H.V. H.). 



b. Median stria: not alternately long and short, 

 a'. Median Stri.e equally shortened, forming a pseudo-stauros ; the 



STRI.T. NEAR THE CENTRAL NODULE ALMOST STRAIGHT. 



N. gracilis KlltZ (Baa, p. 91, pi. 3, f. 48; H.V.H. Atl, pi. 7, 

 f. 7-8*; Type No. 81), plate 3, fig. 109. 



Valve elongate, narrowly lanceolate, with the portion quite terminal, some- 

 times very gently produced, somewhat acute ; striae robust, the 2 or 3 close 

 to the central nodule equally shortened ; the median scarcely radiant, almost 

 straight ; the terminal convergent ; on an average 10 in 1 c.d.m., all reaching 

 to the raphe. Length, 4 to 8 c.d.m. 



Fresh water Antwerp, etc. (H.V.H.), Aid. Lieg. (De Wild.). Found throughout Europe. 



var. schizonemoides H. Van Heurck. (S. neglectum Thwaites 

 H.V.H. Atl., pi. 7, f. 9-10*) plate 3, fig. no. 



Valve usually somewhat narrower near to apices ; median striae longer 

 and of unequal length. Frustules included in mucous tubes. 



Fresh water. Louvain (P. G. ), &c. Bristol, England (Thwaites). 



a' a'. Without false stauros. 

 * Alices not rostrate-capitate. 



N. vulpina KlltZ. (Baa, p. 92, pi. 3, f. 43 (?) ; H.V.H. Atl., pi. 7, 

 f. 18*; in Type No. 132), plate 3, fig. in. 



Large, valve broadly lanceolate, with apices gently produced, rostrate. 

 Central nodule surrounded by a broad hyaline area, sub-quadrangular, 

 rounded. Striae reaching to the raphe, robust, the median ones bent, radiant, 

 the terminal convergent, average number 10 in 1 c.d.m.. Length, about 9 

 c.d.m. 



Freshwater. Ard. Lieg. (DeWild.). Finnety, Scotland. 



N. viridula Kutz. (Baa, pi. 30, f. 47; H.V.H. Atl., pi. 7, f. 25* ; 

 in Type No. 36), plate 3, fig. 115. 



