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NAVICULA. 193
small beads near the raphe. Costas very robust, scarcely radiate, 4.5 to
5 in
1 c.d.m. Intercostal intervals showing coarse beads intermixed with smaller
beads. Length of valve, 10 to 14 c.d.m. Breadth, 3 to 5 c.d.m.
Marine Scheldt, between Antwerp and the sea (H.Y. H. i
Very
rare.
This form has been again reported on our coasts, and belongs to warmer
regions. Possibly it may have been brought by a ship. Pi of. Cleve refers
JV. Beyrichiana to N gemmatula Grun., of which it should be only a variety.
N. splendida Greg. (T.M.S., 1856, iv., p. 44, pi. 5, f. 14 ;
Atl, pi. 9, f. 4* ; in Type No. 104), plate 26, fig. 729.
h.v.h.
Valve elongate, panduriform. Striae 11 to 12 in 1 c.d.m., formed of coarse
beads, separated from the raphe by a broad sulcus, either smooth or furnished
with rudimentary beads. Central nodule quadrangular, surrounded by 4 or 5
robust costae. Length, 12 to 15 c.d.m.
Marine. Scotland. Ireland, and probably elsewhere.
var. Puella Ad. Schm. (Schm. Atl., pi. 12, f. 13*), plate 25, fig. 730.
Valve small, narrow, only showing 2-3 rows of longitudinal costae.
Length, 6 to 10 c.d.m. Breadth, 1*5 to 2-5 c.d.m.
Marine. North Sea.
A A. Valve either furnished with beads or furnished with costa.
N. bomboides Ad. Schm. (N.S. Diat, p. 85, pi. 1, f. 2 ; h.v.h.
Atl. Supp., f. 19* ; in Type No. 74, etc.), plate 3, fig. 146.
Valve elliptic, gently constricted at the median portion. Raphe surrounded
by a narrow hyaline area. Sulci broad, abruptly dilated at the median portion.
more and
Striae straight at the constricted portion, then becoming gradually
more radiate. 4 or 5 in 1 c.d.m., formed of very large beads, subquadrangular,
and almost touching one another, in such a way that the entire surface of the
valve somewhat resembles the paving of a street. Length, about n c.d.m.
Marine. Potter's clay at Ostend (Deby) ; Blankenberghe
(H.V.H.) ;
Shores of the North Sea.
N. didyma Ehr. (Kutz. Baa, p. 100, pi. 4, f. 7: H.V.H. Atl.,
pi. 9, f. 5 and 6; Suppl. f. 20 at another focus*; Type No. 102), plate 3,
fig. 147.
Small, median constriction scarcely pronounced ; sulci straight. Striae
approximate, about 8 in t c.d.m. Length, about 5-5 c.d.m.
Marine. Antwerp (Scheldt), Ostend, Blankenberghe; England (Stolt. , Kitton, Comber, W.
Sm.; Norm.). Rather common throughout Europe.
O