386 



NITZSCHIA. 



Valve narrowly linear, with apices produced ; stria; robust, not interrupted, 

 13 in 1 c.d.m. Length, about 8 to 9 c.d.m. ; breadth, about 1 c.d.tn. 



Fresh and brackish water. Antwerp. England (W. Sm. ). Scotland (Baxter Coll., Nos. 2733, 

 2837). Ireland (O'Meara). 



var, curta. (H.V.H. All., pi. 57, f. 25*; Type No. 376), plate 15, 

 fig. 499. 



Valves much shorter, with apices somewhat rostrate. 



Fresh water. Brussels (Delogne). England, France, Denmark, Sweden. 



Group 2. Panduriformes. 



Valves broad, constricted at the median portion, showing a more 

 or less pronounced sulcus. Keel approximate to one of the margins, 

 with dots either very distinct or apparently absent. Stria; decussate. 



ANALYSIS OF SPECIES. 



f Sulcus very deep, carinal dots very distinct N. panduriformis. 



(^Sulcus indistinct, carinal dots not distinct . N. constricta. 



N. panduriformis Grun. ! (Diat. Clyde, pi. 6, f. 102 ; h.v.h. 



Atl., pi. 58, f. 1-4*; Type No. 377 forma), plate 15, fig. 500. 



Valve broadly elliptic, with apices subrostrate, cuneate ; sulcus strongly 

 marked, and bordered with a hyaline line or irregularly punctate ; striae 

 decussate, 14 to 19 in 1 c.d.m. Carinal dots well marked, about 6 in 

 1 c.d.m. Length, 8 to 12 c.d.m. Breadth, about 2 c.d.m. at the median 

 constriction 



Marine. Not yet found in Belgium. England (Greg., Stolt. ), Bahnsie (Lagers). 



N. constricta (Greg.) Grun. ! Arct. Diat., p. 71; h.v.h. 

 Atl., pi, 58, f. 8*), plate 15, fig. 501. 



Differs from the preceding species by its coarser puncta, its more 

 pronounced sulcus, and by the dots of th2 keel which are not distinct 

 Length, about 5 c.d.m. 



Marine. Scheldt. England. 



forma parva. (H.V.H. Atl., pi. 58, f. 8*), plate 15, fig. 502. 



Very small, only attaining a length of about 1*5 c.d.m. Striae, 16 or 17 

 in 1 c.d.m. 



