196 NAVICULA. 



raphe; 6 or 7 striae in 1 c.d.m., indistinctly resolvable and crossed by a long 

 smooth sulcus, approximate to the margin of the valve, the outline of which it 

 follows. Central nodule large, quadrangular. Length, 6 to 9 c.d.m. Breadth, 

 2 - 25 to 2 - 5 c.d.m. 



Marine. North Sea. 



N. Chersonensis Grun. (Ad. Schm. Atl., pi. 12, f. 40*), plate 

 26, fig. 738. 



Valve parduritorm, with sub-cuneate segments. Striae 8 to 13 in 1 c.d.m., 

 more or less resolvable, continuing in the sulci and approximate to the raphe, 

 feebly radiant, the median straight, more compact than the others. Striae 

 crossed by 2 to 5 longitudinal lines, more or less arcuate. Central nodule 

 large, quadrangular. Length, 5-5 by 15 c.d.m. Breadth of segments, 1 to 3 

 c.d.m. 



Marine. North Sea, &c. 



N. musca Greg. (Diat. of Clyde, p. 7, pi. 1, f. 6*; Ad. Schm. 

 Nordsee, pi. 1, f. 15*), plate 26, figs. 734 and 735. 



Valve conspicuously constricted with subtriangular lobes, apices cuneate. 

 Striae leebly radianc, 7 in 1 c.d.m., occupying only a moiety of the valve, and 

 formed usually of 4 or 5 small beads arranged in two rows, separated by a 

 longitudinal sulcus. Central nodules small, elongated. Raphe surrounded 

 by a very broad hyaline area, dotted here and there with the rudiments of 

 beads. Length, 5 to 6 c.d.m. Breadth, about 2 c.d.m. at the constriction. 



Marine. Scotland, Ireland, Norway. 



N. Eudoxia A. Schmidt. (Atl, pi. 8, f. 39 and 40*), plate 26, 



fig- 739- 



Valve elliptic, linear, scarcely if at all constricted at the median portion, 

 apices obtuse, rounded. Central nodule large, quadrangular, raphe surrounded 

 by a broad sulcus, showing rudimentary costae or a line of beads. Costa? 

 robust, slightly radiate, 6 in 1 c.d.m. Length, 7 to 9 c.d.m. Breadth, 2-5 

 c.d.m. 



Marine. Maritime Scheldt, rare (H.V.H.). Ireland (O'M.), Solsvig (Ad. Schm). 



N. Eugenia Ad. Schm. (Atl., pi. 8, f. 44*), P^te 26, fig. 740. 



Closely allied to the preceding, from which it differs by its size, often very- 

 small, by the sulcus surrounding the raphe, which is quite smooth, and by a 



