370 SURIRELLA. 



var. amphioxys. (S. amphioxys IV. Sm.). Very small ; with valves 

 linear, apices cuneate, more or less acuminate rostrate. 



Fresli water. France (De Brdb.), England (Carrington, Okeden), Aboyne, Scotland 

 (Baxter Coll., 2920), Ireland (Arnott in Baxter Coll., 2817). 



S. linearis W. Sm. (S.B.D., i., p. 31, pi. 8, f. 58a*), plate 31, 

 fig. 864. 



Differs from S. biseriata, of which it is probably only a variety, by its 

 smaller and narrower valves and apices equally rounded, sub-obtuse. 



Fresh water. Belgium (not yet found), England (Kitton, Comber, Norman), Scotland (Dickie), 

 Ireland (O'Meara). 



S. Smithii Ralfs (in Pritch. Inf., p. 794 ; 6". constricta IV. Sm. ! ; 

 S.B.D., i, p. 31, pi. 8, f. 59*), plate 31, fig. 865. 



Valves lanceolate, with apices cuneate, slightly obtuse, often constricted at 

 the median portion ; costas delicate, about 4-5 in 1 c.d.m. Pseudo-raphe 

 narrow, linear in the constricted valves ; lanceolate in the valves not con- 

 stricted. Girdle face linear, with apices truncate, angles rounded, alae very 

 conspicuous. Length, 7 to 14 c.d.m. 



Brackish water. England (W. Sm. ! Comber, Stolt.), Ireland (O'Menra). 



a a. VALVE OVAL, ONE OF THE APICES MOKE OK LESS ACUTE, 



THE OTHER OBTUSE. 



S. elegans Ehr. (Verb., p. r 3 6, pi. III., i, f. 22; h.v.h. Atl., 



pi. 71, f. 3*; Type No. 419), plate 12, fig. 576. 



Valve more or less broadly oval, very large, with median line narrow, 

 surrounded by a hyaline area, lanceolate, broad, with rather strong costse, 

 about 1 "5 in 1 c.d.m. ; striae fine, excessively delicate, 22 in 1 c.d.m. Girdle 

 face cuneate, with apices obtuse, rounded ; alae rather robust, very approxi- 

 mate to the margin. Length, 18 to 22 c.d.m. 



Fresh water. Brussels (Del.), Aid. Lieg. (De Wild.), Devizes, England (Baxter Coll., 2683), 

 Hull (Norman), Ireland (O'Meara), Loch Kinnord, Scotland (Temp, and Per., No. 4), Elgin, 

 Scotland (Arnott in Baxter Coll., 2820). 



S. subsalsa W. Sm. ! (S.B.D., i., p. 34, pi. 31, f. 259*), plate 

 31, fig. 866. 



Resembles considerably a miniature or reduced form of S. Splendida. 

 Valves very small, more or less broadly oboval, with costag rather robust, 3 in 



