A. DE BREBISSON ON SOME FRENCH DIATOMACE.E. 



tained the frustules, .which would consequently have belonged to 

 the genius Homeocladia. This opinion was the result of an in- 

 complete observation. These felted layers supplied the diatom 

 with an accidental station, but were not a part of their indi- 

 viduality. 



Nitzschia gracilenta Grun. in. litt. Found in November, 1868, 

 in pools near Falaise, on a clayey soil. 



Fragilaria virescens Ralfs. Remarkable in this state on account 

 of its numerous sporangiferous articles, half as long again as the 

 frustules, which are disposed in series, and present the most varied 

 forms. 



Eupodiscus Gregory anus. Breb. MSS. Cherbourg. This 

 species is probably Eup. subtilis of W. Gregory, (Diat. Clyd., p. 29, 

 tab. iii., f. 5.) but it may be doubted, for the figure indicates a 

 kind of central nodule, and does not mention the series of small 

 protuberances (processes) which are placed near the edge of the 

 valves. It is this species which was first indicated by W. Smith, 

 under the name of Coscinodiscus concinnus. It cannot be referred 

 to Ehrenberg's Coscinodiscus concinnus, and therefore it seems to 

 me better to give it a new name. 



Eupodiscus Roperii Breb. MSS. Coscinodiscus ovalis. Bop. 

 This species, like the preceding, ought to belong to the genus 

 Eupodiscus. Its texture is the same, and its valves also bear, near 

 their edge, a row of small protuberances or salient appendices 

 (processes), which have no communication with the centre by 

 means of radiating lines, as in the genus Aulacodiscus. 



This is certainly Roper's Coscinodiscus ovalis (Journ. Micr. 

 Sc, vi., p. 3, f. 4.) In truth, in the figure given (b.c), the inter- 

 marginal processes are not indicated, and they may have escaped 

 t}ie draughtsman's observation if he had under his eyes a balsam 

 preparation, as this renders these organs too transparent. 



This species, and the preceding, ought to belong to the genus 

 Cestodiscus, founded by Greville. — (Trans, of Micro. Soc, N.S., 

 vol., xiii., p. 48.) 



Cyclotella rectangula Breb. (Cycl. operculata /3. rectangula 

 Kiitz. Spec. Alg., p. 19.) — I first collected this Diatom near 

 Lagny, in the environs of Paris, and we have since found it 

 around Falaise. It differs much from Cyclot. operculata ; its valves 

 are plane and not undulating ; their contour is strongly marked 

 with points or dimples which are very apparent, even on the very 

 squarely angular edge of the frustules ( front view). 



