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Notes on some French Diatomace.e, Presented to the Club 

 by Alph. de Brebisson, Corr. Mem. 



(Communicated February 25th, 1870. ) 



Pleurosigma JEstuarii. W. Sm. — Mortalines, near St. Vaast 

 (Manche). In these two preparations there will also be remarked 

 the Amphora membranacea, Nitzschia spathulata, and even a few 

 individuals of Toxonidea falcata and insignis. 



Pleurosigma gracilentum Rabenh. P. Kiitzingii Grim. This ought 

 to be the P. Spencerii of W. Smith's Synopsis, but it is not Bailey's 

 species, according to his own examination. 



Navicula (Pinnularid) dactylus. Ehrb. One of the principal 

 forms of the group which includes the Navicula or Pinnularia nobilis, 

 major, etc., which, doubtless, all have the same origin, as coming 

 from the N. viridis Ehrb. (Infus. vol. xiii., f. xvi.) 



Navicula punctata (W. Arnott, in litt.) This species, which is 

 always mixed with many other Diatornacea?, is easy to distinguish 

 by the three enlargements, one of which is central, and two terminal, 

 all rounded, and nearly of the same volume, and especially by its 

 carapace covered with punctuations or rugosities, which appear to 

 be internal. It is this species to which I had in 1828 (" Consid. 

 sur les Diatom, p. 19) given the name of Frustulia acrosphceria, 

 but it is not the Navicula aero splicer ia of Kiitzing (Bacill., p. 97, 

 tab. 5, f. ii.), the summits of which are not sensibly enlarged, nor, 

 as some authors have thought, the Nav. tabellaria of Ehrenberg, 

 which has no punctuations. To avoid a confusion, which is always 

 to be regretted, Walker- Arnott proposed to give to this species the 

 name of Navicula (or Pinnularia) punctata, an opinion which I 

 hastened to adopt, supported by so competent an authority. 



Navicula humerosa Breb. (in W. Sm. App.) This species, which 

 I first found at Divas, in the sandy pools of the sea shore, is pretty 

 common between Trouville and Honfleur in the pools or pits of 

 slightly brackish water with stony bottom. 



It much resembles the Nav. granulata, but the valves of the latter 

 are more elongated, less suddenly attenuated at the summit, often 



