NAVICULA. 171 



with apices somewhat capitate, feebly radiate, 8 in 1 c.d.m. Girdle face 

 contracted, apices truncate. Length, about 7 c.d.m. 



Marin.e Not yet found in Belgium, England, Ireland and Fiance. 



Var. subretusa. (N. subretusa Grun! in Type No. 74. H.V.H. 

 Atl. Supp., f. 10*, in Type No. 74) plate 2, fig. 80. 



Valves narrow ; 6 striae in 1 c.d.m., with non-capitate apices. 

 Length, about 7 c.d.m. 



Marine. Blankenberghe, in the sand of the shore. 



N. Hilseana Janisch. (in Schmidt. Atl., pi. 45, f. 65, etc. H.V.H. 

 Atl., Supp., f. ir,* in Types Nos. 39 and 347) plate 2, fig. 81. 



Valve linear, with rostrate-capitate apices. Raphe without hyaline zone ; 

 Central nodule surrounded by a pseudo-stauros rather broad, sub-cuneate. 

 Striae rather feeble 10 in 1 c.d.m. ; radiate in the centre, convergent at the 

 apex of the valve. Length, about 4 c.d.m. 



Fresh \vater.--Paliseul (Delogne). 



aa. COST/E NOT REACHING THE RAPHE THROUGHOUT, THOSE IN THE 

 MIDDLE OF THE VALVE CONSIDERABLY SHORTENED OR ABSENT. 



b. Valves o?dy slightly or not inflated at the median portion. 



N. Brebissonii Kiitz. ! (Bac. p. 93, pi. 3, f. 49; H.v.H. Atl, 

 pi. 5, f. 7* ; Type No. 58) plate 2, fig. 82. 



Valve linear-elliptic, with apices rounded, somewhat diminuate. Raphe 

 surrounded by a hyaline zone, narrow towards the apices, infmitesimally 

 dilated towards the median portion. Costae well marked, shortened towards 

 the median portion and absent in the middle of the valve, where their absence 

 forms a false stauros ; costae rather strongly radiate up to nearly the extreme 

 third of the valve where they suddenly become strongly convergent, 11 in 1 

 c.d.m. Length, 4 to 5 c.d.m. 



Fresh water. Common throughout Europe. 



Var. subproducta. (H.V.H. Atl., pi. 5, f. 9*), plate 2, fig. 83. 

 Broader and shorter, with apices somewhat diminuate sub-rostrate. 



Park, near Louvain. 



Var. diminuta. (H.V.H., pi. 5, f. 8*), plate 2, fig. 84. 



Slender, very small, apices infmitesimally diminuate. 



Frahan (Delogne). 



N. Stauroptera Grun. (ijber neue etc. fam. Navicula, p. 517. 

 H.V.H. Atl., pi. 6, f. 7*) plate 2, fig. 85. 



Valve linear-elongate, scarcely inflated at the median portion, with 

 apices rounded, inflated. Costae radiate at the median portion, strongly 

 convergent at apices ; robust, leaving throughout a considerable hyaline 



