SYNEDRA. 309 



III. TOXARIUM. Valves very narrow, but strongly inflated at the 



median portion and at the apices and covered with 



irregular puncta, no sulci. 



Valve strongly undulated throughout its length . . . S. uiidulata. 



Valve not undulated . . . . . S. Hennedyana. 



I. EUSYNEDRA. Valves scarcely or not inflated in the middle, 



regularly striated. 



* Valve without marginal sulci. 



A. ST RLE EXTENDING THROUGHOUT THE WHOLE VALVE. 



a. Valve furnished with an annular pseudo-nodule. 



S. pulchella Kutz. (Baa, p. 6S, pi. 29, f. 87 ; H.V.H. Atl, pi. 40, 

 f. 28 and 29* ; Type No. 298), plate 10, fig. 402. 



Valve narrowly lanceolate, with apiees gently rostrate-capitate, pseudo- 

 nodule strongly marked, often reaching to the margin. Pseudo-raphe narrow, 

 terminated by small but distinct nodules. Stria;, 13 or 14 in 1 c.d.m., distinctly 

 punctate. Girdle face narrow, linear, attenuate at the apices. Frustules 

 forming flabella. Length, about 6 c.d.m. 



Fresh (?) and brackish water. Antwerp, Blankenberghe, (H.V.H.) Ard. Lieg. (De Wild.). 

 England (Kitton, Comber, Noiman, Grove), Scotland, Ireland (O'Meara), France. 



forma major. (H.V.H. Atl., pi. 40, f. 27, and plate 4r, f. 1*) plate 

 10, fig. 403. 



Much larger and attaining to more than 12 c.d.m. 



var. Smithii Ralfs. (S. acicularis IV. Sm , H.V.H. Atl., pi. 41, f. 2* ; 

 Type No. 300) plate 10, fig. 404. 



As long as the major form, but much narrower. Stria; 14 or 15 in 1 



c.d.m. 



Fresh water. Antwerp, Ireland. Brackish water. England (W. Sm., Kitton, Stolt. , 

 Norman, Grove), Ireland (O'Meara). 



var. lanceolata O'Meara. (S. minutissima W. Sm. ; H.V.H. Atl., 

 pi. 41, f. 7* ; Type No. 299) plate 10, fig. 405 



Much smaller than the type form, about 3^5 c.d.m., and proportionately 

 broader, almost naviculoid ; 15 striae in 1 c.d.m. 



Fresh water. Antwerp. England (W. Sm., Norman, Comber), Ireland. 



var. vertebra. (S. vertebra Greg.) Q.J. M.S., 1855, p. 41, pi. 4, f. 22). 



Valve large ; broad at the median portion, then becoming narrower up 

 to the apices. 



Lacustrine deposit. Scotland, 



