1 82 NAVICULA. 



Differs from the preceding species, of which perhaps it is only a variety, 

 by its very feeble striae, sometimes scarcely visible and scarcely radiant, 

 almost straight, about tS in 1 c.d.m. Length, about 2*5 c.d.m. 



Brackish w.iter. Common : Antwerp (Austruweel), Blankenberghe. England. France. 



The apices are sometimes simply rostrate, scarcely capitate (Blankenberghe), 

 sometimes strongly capitate (Antwerp). 



AA. Striae very distant and very robust, very small forms with terminal nodule 



like a hook. 



N. costulata Grun. ! (Arct D., p. 27 ; H.V.H. Atl. Su PP ., f. 15* ; 

 Type No. 71), plate 3, fig. 126. 



Small, rhomboidal lanceolate, costae reaching to the raphe, very robust, 

 very distant (7 or 8 in 1 c.d.m.), strongly radiant at the median portion, 

 convergent near the apices, 5 to 7 on each quarter of the valve ; absent at 

 the median portion, where they leave a very broad stauroneiform hyaline 

 space. Terminal nodules like hooks. Length, 1*25 to 1*5 c.d.m. 



Fresh water Rouge-Cloitre (Delogne). 



N. humilis Donk. (Brit. Diat., p. 67, pi. 10, f. 7. JV. inflata 

 IV. Sm., nee Au/z.H.V.R. Atl., pi. n, f. 23*; Type No. 70), plate 3, 

 fig. 127. 



Valve linear, very inflated at the median portion, with apices rostrate 

 capitate, truncate, rounded. Raphe not surrounded by a hyaline area. 

 Costa? very robust, 8 in 1 c d.m., radiant at the median portion, convergent 

 at the apices. Terminal nodules like hooks. Length, 1*5 to 2 c.d.m. 



Fresh water. Common. Antwerp, Brussels (H.V.H. ), Aid. Li6g. (De Wild.), England. 



These two forms, which are very closely allied, have hitherto been 

 mixed up with the Pinnulariae ; by examining them in the yellow medium 

 of Prof. H. L. Smith, I have been able to demonstrate that they are 

 clearly Radiosae, but with strise very difficult to resolve into beads. One 

 figure is a little defective, there ought not to be a hyaline area round the 

 central nodule. 



N. nana Greg.! (qj.m.S. 1856, iv., p. 3, pi. 1, f. 8), plate 

 25, fig. 711, after a photograph by H.V.H.* 



Valve minute, oval elliptic, with apices rounded, obtuse ; striae reaching 

 almost to the raphe, very radiant ; the median ones simulating a schizo- 



