NAVICULA. 183 



stauros in consequence of their distance from one another, 10 or 11 in 1 

 c.d.m. Terminal nodules like hooks. Length of valve, 2 to 3 c.d.m. 

 Breadth, 1 c.d.m. 



Fresh water. Near Edinburgh, Scotland (Gregory !). 



II. Median stria: radiant, the terminal ones perpendicular to the raphe 



(straight). 



N. cancellata Donk. (Brit. Diat., p. 55, pi. 8, f. 4a and 4b. ; 

 H.V.H. Atl. Supp., f. 16*; Type No. 73), plate 3, fig. 128. 



Valve narrow, linear or linear lanceolate, with apices tapering, acute or 

 sub-acute. Raphe surrounded by a narrow hyaline zone, somewhat 

 enlarged near the central nodule. Stria? very distant, 6 or 7 in 1 c.d.m.. 

 faintly divided cross-wise, radiant at the median portion of the valve, 

 perpendicular near the apices. Girdle face constricted in the middle. 

 Length, 5-5 to 7 c.d.m. 



Marine. Not yet found in Belgium. England, Scotland, Ireland, France. 



var. ammophila Grun. (Oest. Foss. Diat.. p. 14, pi. 2, f. 66-67*; 

 in H.V.H. 's Types Nos. 1 1, 94, 116), plate 25, fig. 712. 



Small, narrow, striation approximate, 10 or 11 in 1 c.d.m. at the 

 median portion, 12 or 13 at the apices. Length, 175 to 3 c.d.m. 



Marine and fresh water Antwerp in Belgium. Creswell, Northumberland, England. 



var. Scaldensis H.V.H. (Atl. Supp., fig. 17*, in Type No. n), 

 plate 3, fig. 129. 



Narrowly lanceolate, with apices attenuate-sub-rostrate. Striae 9 to 1 1 

 in 1 c.d.m. at the median portion of the valve. Length, 4-5 to 5*5 

 c.d.m. 



Brackish water Antwerp. 



N. cancellata is not a true Radiosa. It ought to form, with allied 

 forms, a special group, intermediate between the Pinnularise and the 

 Radiosae. The same is true of JV. humids and cosiulata. 



N. crucifera Grun. ! (in Ad. Schm. Atl., pi. 46, f. 50-54*), plate 



25, fig. 710. 



Valve lanceolate with apices cuneate, rostrate-acute. Transverse striae 5 

 or 5 - 5 in 1 c.d.m., distant, robust, finely divided cross-wise, not reaching to the 

 raphe, all radiant ; the two median ones equally shortened and leaving an 

 elongated stauroneiform hyaline space. Length of valve, 3 to 5-5 c.d.m. 

 Breadth, about 1*5 c.d.m. Girdle face subquadrangular with somewhat con- 



