160 STAUR0NE1S. 



tabular, showing the thickening of the internal apices of the valves and the 

 connecting zone plicate-punctuate. Length, 8 to 15 c.d.m. 



Fresh water. Everywhere, but not so frequent as St. Phcenicenteron. 



S. Gregorii Ralfs. (in Pritch., p. 913. S. amphioxys Greg, T.M.S., 

 1856, p. 4S, pi. 5, f. 23 ; H.V.H. Atl., Suppl. f. 4* ; in Types No. 74 and 389) ; 

 plate 1, fig. 52. 



Valve lanceolate, with apices subrostrate ; more or less obtuse and show- 

 ing a rather small lumen ; raphe simple ; stauros very broad ; striae finely 

 granular, slightly radiant, delicate, about 18 to 20 in 1 c.d.m. Length, about 

 8 c.d.m. 



Brackish water Biankenberghe (rare?). England (Kitton). Scotland (Greg.). 



** Stauros very narrow, raphe simple. 



S. Spicula W. J. Hickie. (Monthly Micro. Journ., 1874, xii., 

 p. 290; H.V.H. Atl. pi. 4, f. 9* : in Type No. 9), plate 1, fig. 53. 



Valve very narrowly lanceolate, infinitesimally attenuate as far as the 

 subacute apices ; stauros very narrow, not dilated at the extremities ; raphe 

 simple, surrounded by a narrow hyaline zone ; striae delicate, scarcely radiant, 

 28 in 1 c.d.m. Length, 5 to 8 c.d.m.. 



Brackish water. Very rare? Antwerp, Biankenberghe. England, Swansea Dock (Okeden 

 in H.V H., Type No. 9), Norfolk (Kitton). 



S. salina W. Sm. (s.B.u. i., p. 60, pi. 19, f. 188; h.v.h. Atl., 



pi. 10, f. 16*; Type No. 44), plate 1, fig. 54. 



Valve rather broadly lanceolate, with apices sometimes slightly produced- 

 rostrate ; stauros narrow, only slightly or not enlarged at extremities ; stria? 

 delicate, finely punctate, scarcely radiant, about 18 in t c.d.m. Length, about 

 5 to 6 c.d.m. ; breadth, 0.5 c.d.m. 

 Marine. Biankenberghe, Antwerp, England, Ireland, Denmark. 



b. VALVES WITH APICES ROSTRATE OR ROSTRATE-CAPITATE. 



S. ancepS Ehr. (Verb., p. 134, pi. ii., 1, 18; H.V.H., Atl. pi. 4, 

 f. 4, 5*; Type No. 43), plate 1, fig. 55. 



Valve elliptical or elliptical-lanceolate, with apices rostrate-capitate ; stauros 

 broad, dilated near its extremities ; raphe simple, surrounded by a broad 

 hyaline zone; striae delicate, strongly radiant, about 20 in 1 c.d.m.; length, 

 3.5 to 5 c.d.m. 

 Fresh water. Everywhere (but not very abundant?). 



Var. linearis. (S. linearis KUtz. H.V.H. Atl., pi. 14, f. 8*); plate i, 



fig. 56. 



Valve with parallel margins ; apices abruptly attenuate-rostrate. 



