314 SYNKDRA. 



A A. STRL MARGINAL, OR AT LEAST THE PSEUDO-RAPHE ENLARGED AT 

 THE MEDIAN PORTION AND CONSEQUENTLY LANCEOLATE IN FORM. 



S. affinis KutZ. ! (Bac, p. 68, pi. 15, f. 6 and 11 ; H.V.H. Atl., pi. 4', 



f. 13*; Type No. 302 and in various type slides), plate 10, fig. 430. 



Valve lanceolate, with apices sometimes slightly rostrate-capitate ; striae 

 marginal, leaving a considerable lanceolated pseudo-raphe, rather fine, 13 or 

 14 in 1 c.d.m. Length, 9 to 12 c.d.m. 



Marine and brackish water. Blankenberghe. England (Kitton, Comber, Norman, Stolt.). 

 Scotland (Baxter Coll., No. 2830). Ireland (O'Meara). Throughout Europe, 



var. tabulata. (S. tabulata Kiilz. ; H.V.H. Atl., pi. 41, f. 9A* ; in 

 Types Nos. 102, 174, and 234), plate 10, fig. 431. 



Valve more longly lanceolate ; striae more shortened, about 9*5 in 

 1 c.d.m. 



Same habitat. 



var. parva Kiitz. (.9. parva Kiiiz. ; H.V.H. Atl., pi. 41, f. 23*), 

 plate 10, fig. 432. 



Very small (about 3 to 7 c.d.m.), with striae fine, approximate, 19 to 21 

 in 1 c.d.m. 



Same habitat. 



These three forms pass into one another by every graduation. 



var. fasciculata. (S. fasciculata K'utz. ; H.V.H. Atl., pi. 4r, f. 15*; 

 Type No. 302), plate 10, fig. 433. 



Valve rather broadly lanceolate, with pseudo-raphe lanceolate, narrower 

 than in the preceding forms. 



England (W. Sm., Norman). Scotland (Baxter Coll., No. 2524). 



S. nitzschioides Grun. (Oest. D., 1862, p. 89, pi. 8, f. 18*; 



Thalassiothrixl nitzschioides Grun.; H.V.H. Atl., pi. 43, f. 7-10*), plate 10, 

 fig- 434- 



Valves linear, narrow, or more or less lanceolate, with apices acute or 

 obtuse ; pseudo-raphe very broad. Valves showing on their margins coarse 

 beads, 10 to 12 in 1 c.d.m., very distinct, and between these are often found 

 short indistinct striae. Frustules rectangular in girdle view, united into a 

 filament, arranged sometimes in stellate forms, as in an Asterionelia. Length, 

 4'5 to 7 c.d.m. 



Marine. Basin at Blankenberghe Rare. Scheldt (pelagic, very frequent, H.V.H.). Ireland, 

 (O'Meara). 



This diatom is not a true Synedra. Perhaps a new genus should be 

 created for it. 



