NAVICULA. 22 7 



a a. Valve without costae. 



b. VALVE FURNISHED WITH A PSEUDO-STAUROS 



N. Seminulum Grun. ! (H.v.H. Atl., pi. 14, f. 9*; Type No. 

 143), P la *e 5, fig- 228. 



Valve almost linear, with median portion inflated, apices obtuse rounded ; 

 striae radiate, rather robust, punctate, 20 in 1 c.d.m., reaching almost to the 

 raphe, much shortened near the central nodule, where their limited length 

 produces a stauroneiform blank space. Length, about 1.5 c.d.m. Breadth 

 4 c.d.m. 



Fresh water. Brussels (Delogne). 



N. minima Grun. ! (H.v.H. Atl., pi. 14, f. 15*; Type No. 142), 

 plate 5, fig. 229. 



Valve linear, with rounded apices ; stria? radiate, 26 in 1 c.d.m, reaching 

 to the raphe, the median ones much shortened, and considerably more distant. 

 Length, 1*5 c.d.m. Breadth, '45 c.d.m. 



Fresh water. Brussels, in a water bottle (Del.). 



N. atomoides Grun. ! (H.V.H. Atl., pi. 14, fig. n*; in Type No. 

 219), plate 5, fig. 230. 



Valve elliptic ; striae fine, feebly radiate, 27 to 30 in 1 c.d.m,, reaching 

 almost to the raphe, but shortened near the central nodule, where they form 

 a pseudo-stauros of greater or less length. Fruslules often united into a band 

 of 3 or 4. Length, about '8 c.d.m. Breadth, about '4. c.d.m. 



Fresh water. Antwerp, in an aquarium, where the species has been maintained for several 

 years. 



Prof. Cleve makes this form a simple variety of N. minima. 

 b b. VALVE WITHOUT FSEUDO-STAUROS. 



N. Atomus Nsegeli. (H.v.H. Atl, pi. 14, f. 24* ; Type No. 149), 

 plate 5, fig. 231. 



Valve elliptic, feebly silicious ; raphe robust ; striae fine, strongly radiate, 

 about 30 in i c.d.m. Length, *4 to - 8 c.d.m. Breadth, -25 to "4 c.d.m. 



Humid positions. Brussels (Delogne), Antwerp. 



