3 82 



NITZSCH1A. 



H. marina (Donkin) Grun ! (Arct. D., p. 105. Epithemia 



marina Donkin ; H.V.H. Atl., pi. 56, f. 14 and 15* ; Type No. 369), plate 

 15, fig. 489^. 



Valve arcuate, with rostrate apices. Keel with 6 dots in 1 c.d.m., prolonged 

 into delicate costae, which traverse the entire valve, and between each of which 

 are found two rows of fine alternating puncta. Girdle face linear, showing two 

 keels inflected towards the connecting zone. Length, about 6 to 10 c.d.m. 



Marine. Ostend, Blankenberghe (H.V.H), England (Donkin, Comber, Kitton), France (Br6b), 

 Ireland (O'Meara). 



GENUS 81. 



NITZSCHIA (HASSALL, 1845; W. SMITH) 

 GRUNOW Ch. em., 1880. 



Valves furnished with a keel, with carinal 

 dots either short, or prolonged into short 

 cost;e, rarely traversing the entire valve. Keels 

 of the two valves diagonally opposite. Frus- 

 tules free, rarely enclosed in tubes or united 

 into a stratum. 



Endochrome consisting of a single lamina, 

 interrupted partially or entirely at the median 

 portion of the frustule. 



In the classification of this genus I shall follow 

 the excellent monograph published by Mr. Grunow 

 in the Arctische Diatomcen, and I have also 

 borrowed from him a few of his descriptions. 



crr 



Fig. 124. 

 Nitzschia spectabilis. 



