NAVICULA. 203 



A A . Valves with finely punctate stria:. 



N. abrupta Greg. (IV. Lyra vat. abrupta Gre<>. Diat. of Clyde, 

 p. 14, pi. 1, f. 14; H.V.H. Atl., pi. 10, f. 4*; in Type No. 104), plate 4, 

 fig. 162. 



Differs from the preceding by the valves being regularly oval, with apices 

 never diminuate, and by the sulci always recurved on the side of the raphe, 

 and abruptly terminated at a certain distance from the apices. Striae about 



10 in 1 c.d.m. in my specimen, which appears to be smaller than usual. The 

 valve appears colourless when dry. 



Marine. Very rare. Washing of mussels (Debj. ). England, Scotland, Bahnsie. 



N forcipata Grev. (Q.J. M.S., 1859, vii., p. 83, pi. 6, f. 10 and 



11 ; H.V.H. Atl, pi. 10, f. 3 ; in Type No. 104), plate 4, fig. 163. 



Differs from N. Lyra by its smaller size, its striae approximate and finely 

 granulate, and especially by the clavate enlargement (which is characteristic) 

 of the median apices of the raphe. Striae fine, about 15 in 1 c.d.m. Valve 

 brown when dry. 



Marine. Rather common. Scheldt at Antwerp, Blankenberghe. England, Scotland, France. 



N. pygmaea Klltz. (Spec. Alg., p. 77; N. minutula IV. Sm. ; 

 H.V.H. Atl., pi. 10, f. 7*, in Types No. 9, 11, 77, 95, 99, 192, etc.), plate 4, 

 fig. 164. 



Small, valve narrowly elliptic. Raphe surrounded by a hyaline zone, 

 narrow, very much enlarged quite round the central nodule. Striae very fine, 

 about 26 in 1 c.d.m., becoming gradually radiate from the middle of the valve, 

 interrupted on each side of the raphe by a sulcus strongly incurved at the 

 median portion, and of which the apices rejoin the raphe somewhat before 

 reaching the apex of the valve. Length, 2^25 to 4'5 c.d.m. Breadth, 1 to 

 1*25 c.d.m. 



Brackish water. Antwerp, Blankenberghe; England (Kitton), France. 

 Fresh water. Louvain (P.G. ). 



VI. Hennedyeae. 



f Margins of valve with coarse beads ; sulci with coarse scattered beads . N. prsetexta. 



I 



J Margins of valve with coarse beads; sulci finely dotted, showing in the 



middle an arc formed by rovs of 1; to 6 coarse beads . . . N. Sandriana. 



i 



I. Margins of valve with fine beads ; sulci smooth or finely dotted . . N. Hennedyi. 



