394 NITZSCHIA. 



Differs from the preceding species by the apices of the keel, which are 

 much enlarged and elevated. Carinal dots 4 or 5 in 1 c.d.m. Strise 

 excessively delicate. Length, about 10 c.d.m. 



Marine Blankenberghe, Antwerp (Scheldt H.V.H.), France (Br6b.), Denmark (Heib. !), 

 England (Harrison, Norman), Ireland (O'Meara). 



var. hyalina (H.V.H. Atl., pi. 62, f. 9*), plate 16, fig. 524. 



Very small (about 4 c.d.m.), about 7 or 8 carinal dots in 1 c.d.m. 



Same habitat. 



N. distans Greg. (Diat. of Clyde, p. 58, pi. 6, f. 103; H.V.H. 

 Atl., pi. 62, f. 10*), plate 33, fig. 878. 



Valve narrowly lanceolate, with apices somewhat produced, sub-rostrate ; 

 keel central with dots unequally distant, 1*5 to 3 in 1 c.d.m. Stria; excessively 

 delicate and approximate. Girdle face linear, with sub-truncate apices, 

 showing the keel somewhat alate. Length, up to 15 c.d.m. 



Marine. England (Stolt.), Glenshira sand, Scotland (Gregory), Bahnsie (Lagerstedt). 



N. cursoria (Donk.) Grun. (Arct. Diat, p. 89; H.V.H. Atl., 

 pi. 62, f. 19* ; Bacittaria cursoria Do/ik.,) plate 33, fig. 879. 



Valve very narrowly lanceolate, with apices longly rostrate, keel central, 

 narrow, with about 10 dots in 1 c.d.m., accompanied by two accessory lines, 

 distant about -4 c.d.m. Striation very fine. Frustule linear, with truncate 

 apices. Length, 7 to 8 c.d.m. Breadth of valve, 7 c.d.m. 



Marine. England (Donkin, Norman), France (Brb.). 



Group 15. DlSSIPAT/E. 



Differs from the two preceding groups by the keel being less 

 central and the absence of auxiliary lines. Valves very small and 

 very delicately striated. 



ANALYSIS OF SPECIES. 

 Keel not quite central. Valves very small and delicately striated . N. dissipata. 



N. dissipata (Kiitz.) Grun. ! (Arct. Diat, p. 90; N. 



minutissima W. Sm. ? H.V.H. Atl., pi. 63, f. 1*; Type No. 391), plate 16, 

 fig- 525- 



