l8o NAVICULA. 



Valve broadly lanceolate, with apices tapering, rostrate, obtuse. Central 

 nodule surrounded by a broad rounded hyaline area. Striae robust, reaching 

 to the raphe, the median ones radiant, about 8 in i c.d.m. ; the terminal 

 convergent, 10 in i c.d.m. ; terminal nodules robust. Length, about 7 c.d.m. 



Fresh water. Brussels (Delogne). Throughout Europe. 



forma minor. H.V.H. At!., pi. 7, f. 26*), plate 3, fig. 116. 



Smaller with more rostrate apices. 



var. avenacea. (N. avenaaa Breb. ; H.V.H. Atl., pi. 7, f. 27*; 

 Type No. 8S), plate 3, fig. 117. 



More lanceolate ; apices more narrowly rostrate. Length, about 5 

 c.d.m. 



Fresh water. Brussels (Del.). Ard. Lieg. (DeWilri.). Pentland Hills, Scotland. 



var. Slesvicensis (IV. Shsvicensis Gri/n.f); H.V.H. Atl., pi. 7, 

 f. 28 and 29* ; Type No. 89), plate 3, fig. 118. 



Small, rather broadly lanceolate, apices conspicuously rostrate with a 

 broad rostrum. Striation as in the type form, 8 or 9 stria? in 1 c.d.m. 

 Breadth, 3 to 5 c.d.m. 



Fresh and brackish water. Rather common. Antwerp (Scheldt), Louvain (P.G. ), &c. 

 Stoneferry, near Hull, Duddington Lock, Northamptonshire (England). 



N. radiosa Kutz. (Baa, p. 91, pi. 4, f. 23; H.V.H., pi. 7, f. 20* ; 

 Type No. 85), plate 3, fig. 112. 



Valve lanceolate, narrow, slightly attenuate, with apices very gently sub- 

 capitate. Central noduie surrounded by a very small hyaline area. Median 

 striae bent, very radiant, the terminal ones convergent; about n or 12 stria? 

 in 1 c.d.m. Frustules, narrow in girdle view, with apices diminuate. Length, 

 4 - 5 to 6 c.d.m. 



Fresh water. Common throughout Europe. 



var. acuta. (Pinnularia acuta, IV. Stn.; H.V.H. Atl., pi. 7, f. 19* 

 Type No. 86) ; plate 3, fig. 113. 



More elongated, more narrowly lanceolate, and with apices more acute 

 Length, about 8 to 9 c.d.m. 



Fresh water. As the preceding form with which it is often mixed. 



Var. tenella. (Nav. tenel/a Breb.; H.V.H. Atl, pi. 7, f. 21 and 22*; 

 in Type No. 107), plate 3, fig. 114. 



Differs from the type form in its size, being smaller, its apices more 

 acute, and its striae more delicate and more approximate, 15 to 18 in 

 1 c.d.m. 



Fresh water. Brussels, etc. 



N. cryptocephala Kutz. ! (Bac, pi. 3, f. 26; H.V.H. Atl., pi. 8, 



f. 1 and 5*; in Type No. 25; var. intermedia: Type No. 92; var exilis: 

 Type No. 93), plate 3, fig. 122. 



