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 ; h.v.h. 



Atl, pi. 9, f. 4* ; in Type No. 104), plate 26, fig. 729. 



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. 

 Striae straight at the constricted portion, then becoming gradually more and 

 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 



