LIBELLUS. 235 



N rhombica Greg. (Q.J.M.S., 1S55, iii., p. 40, pi. 4, f. 16 ; Donk. 

 Brit. Diat., pi. 9, f. 1*), plate 27, fig. 783. 



Valve rhombic, lanceolate, strongly convex, with apices acuminate, sub- 

 acute. Transverse striae finely punctate, the median ones somewhat radiate, 

 the others sub-parallel, 16 to 16-5 c.d.m. Length, about 7 c.d.m. Breadth, 

 about 1*5 c.d.m. 



Prof. Cleve considers that this form does not essentially differ from IV. 

 (Schiz.) Grevillei. 



Marine. England, Scotland, Ireland, Denmark. 



N. simulans Donk. (Brit. Diat, p. 60, pi. 9, f. 3*), plate 27, 

 fig. 784. 



Valve linear, with parallel margins, apices cuneate. Stria; very fine, leaving 

 a stauroneiform blank space. Girdle face with apices truncate, rounded 

 angles, somewhat constricted at the median portion. Length, 6 to 7^5 c.d.m. 

 Breadth, 1-5 c.d.m. 



Marine. Xewbiggin, Northumberland (Donkin). 



We give the above description according to Donkin, but we have not seen 

 any authentic specimens. Donkin and other authors connect with this form 

 Amphiprora conslrida W. Sm. This is an error : the forms from Prof. Smith's 

 herbarium are not those of a Navicula. 



N. plicata Donk. (Brit. Diat., p. 59, pi. 9, f. 2*), plate 28, fig. 



787. 



Valve narrow, linear, with subcuneate apices. Strice fine, 20 in 1 c.d.m., 

 not reaching quite to the raphe. Girdle face broad, linear, with apices trun- 

 cate, angles rounded, constricted at the median portion with the connecting 

 zone showing numerous pleats. Length, 8 or 9 c.d.m. Breadth of the valve, 

 i'5 c.d.m., and of the girdle face, 3 c.d.m. 



Marine sands. Warkuorth, Northumberland (Donkin). 



N. COmplanata Griin. (Amphora comp!a?iaia Grun. ; Hedwigia, 

 vi., p. 25 ; Ad. Schm. Atl., pi. 26, f. 45*), plate 27, fig. 785. 



Valve linear lanceolate, acute ; striae 18 or 19 in 1 c.d.m. Length, 3*5 

 c.d.m. Breadth, o # 5 c.d.m. Girdle face rectangular, showing very numerous 

 pleats; breadth, 3-5 c.d.m. 



Marine. Finmark, Sweden (H.L. Sm., Type No. 612 !). 



