326 FRAGILARIA. 



var. binodis Grun. (H.V.H. Atl., pi. 45, f. 24A. and 25*), plate 

 11, fig. 452. 



Valve lanceolate, with apices rostrate, median portion constricted. 



Fresh water. Antwerp, rather common and parasitic on Nitzschia Sigmoidea. Ard. 

 Lieg. (De Wild.). England (Kitton), &c. 



F. tenuicollis Heib. (Consp. Diat. Danic, p. 62, pi. 5, f. 13*), 

 plate 30, fig. 843 and 843 bis. 



Valves very narrowly lanceolate, linear, with apices rostrate-capitate. 

 Pseudo-raphe narrow ; stride very robust, somewhat radiant, convergent, 

 approximate, about 10 in 1 c.d.m. Girdle face quadrangular, very elongated, 

 somewhat produced at the apices. Length, 2*5 to 5 c.d.m. 



Fresh water. Denmark (Heiberg). Ireland (O'Meara). 



var. intermedia (Fr. intermedia Grun. ; H.V.H. Atl., pi. 45, f. 9*), 

 plate 30, fig. 844. 



Only differs from the preceding by the presence of a small median 

 unilateral hyaline space. Striae robust, 9 or 10 in 1 c.d.m. 



Freshwater. England, Ormesby Broad, Norfolk (Kitton in W. Arn. Coll., Nos, 914-915 

 tinder the name of Frag, tenuicollis. ) 



F. Harrisonii (W. Sm.) Grun. ! (Oest. Diat, p. 368; H.V.H. 



Atl, pi. 45, f. 2S* ; Type No. 316), plate 11, fig. 453. 



Valve sub-cruciform, with rounded angles, apices obtuse or sub-obtuse. 

 Pseudo-raphe lanceolate. Striae very robust, 4 or 5 in c.d.m, formed of 

 puncta, confluent and simulating costae. Length, about 2 to 5 c.d.m. 



Fresh water. Very rare. Mountainous parts of Belgium : Bouillon (Delogne). England 

 (W. Sm, Kitton), New River (Grove). 



F. mutabilis (W. Sm.) Grun. ! (Oest. Diat,, p, 369, H.V.H. 



pl. 45, f. 12* ; Type No. 315), plate 11, fig. 454. 



Valves elliptic or, more rarely, linear-elliptic ; striae very robust, with 

 beads confluent, 8 or 9 in 1 c.d.m. Length, 1 to 2*5 c.d.m. 



Fresh water. Brussels (Delogne) Louvaine (P.G.) Ard. Lieg. (De Wild.). England (Kitton), 

 New River (Grove). 



F. brevistriata Grun. ! (H.V.H. Atl, pi. 45, f. 32*; Type No. 

 31S), plate 11, fig. 455. 



Valve lanceolate, with apices produced rostrate ; striae very short and 

 marginal, 13 or 14 in 1 c.d.m. Length, 1*25 to 2 c.d.m. 



Fresh water. Brussels (Delogne). Ard, Lieg. (De Wild.). 



