2 A. DE BREBISSON ON SOME FRENCH DIATOMACE.E. 



contracted towards the middle, and charged with more pronounced 

 and more distinctly moniliform striae 



Navicula oculata Breb. (in Desm. Crypt., 110) First discovered 

 by the learned algologist, M. G. Thuret, near Lagny, in the 

 environs of Paris ; this species has since been collected by us near 

 Falaise. It is very small, linear, with rounded summits, and re- 

 markable by its very apparent central nodule. 



Peronia erinacea Breb. and W. Arm (in Journ. Micr. Sc.) 

 Different characteristics, and principally the absence of a central 

 nodule on the valves, not permitting this Diatom to be retained 

 in the genus Gomphonema, where I had first placed it (see Kiitzing, 

 Sp. Alg. p. c g, sub. Gomph. Fibula) have determined W. Arnott and 

 myself to propose this new genus which at present contains but one 

 single species which grows in fresh water springs, on inundated 

 plants, and especially on the leaves of Sphagnum. 



Cymatopleura apiculata W. Sm. et var. We do not think that 

 this Cymatopleura can be anything but a variety of C. Solea. All 

 the forms presented by this species pass so much from one to the 

 other in an insensible manner that it would be always difficult to 

 assign them a place in a regular series. The forms included in the 

 accompanying preparation are the var. apiculata and another 

 larger, broader, figured by Ehrenberg in his large work on the 

 Infusoria (t. xiii., xxii., f. 1 and 3) and which, for this reason, 

 I call var. Ehrenbergii. Fig. 2 of the same plate must be the 

 variety Lib rile. 



Surirella Capronii. I am indebted to Mr. Fr. Kitton for the 

 knowledge of this remarkable Diatom. Having communicated to 

 him, nearly two years ago, the mixture of Surirella which had been 

 collected in our neighbourhood, he observed to me that, in the 

 midst of the numerous individuals of Sur. elegans which were most 

 prevalent, there was another form, the valves of which were pro- 

 vided on their broadest summit with a sort of spur, or salient point, 

 and informed me at the same time that a similar form had been 

 noticed in England by Dr. Capron, the naturalist, who is so often 

 mentioned by W. Smith as having communicated to him interesting 

 researches in the neighbourhood of Guildford. Dr. Capron having 

 been so good as to address to me a preparation of his curious 

 Surirella^ I was able to convince myself of its identity with the 

 Normandy plant ; 1 then proposed to dedicate it to Dr. Capron. 

 I have since received from the clever Danish preparer, M. Mollcr of 



