ill!Ill

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. !
25, fig. 710.
(in Ad. Schm. Atl., pi. 46, f. 50-54*), plate
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-