2 Prof. W. Smith on the Diatomacese of the Pyrenees. 



were almost identical with those already familiar to me on the 

 southern coasts of England ; but a fountain in the court of the 

 hotel (Frascati) at which I sojourned, supplied a form which was 

 different not merely in species, but in genus, from any I have 

 hitherto recorded as British ; this was the Diadesmis described 

 in a subsequent part of the present paper. From an oyster 

 tank at St. Adress, about a mile north of Havre, I also made a 

 gathering, which, on being prepared for mounting, supplied 

 numerous valves of Zygoceros Surirella. This species I have 

 placed in Appendix B. of the ' Synopsis of the British Diato- 

 macese,' as described and figured by Mr. Boper in the ' Trans- 

 actions of the Microscopical Society,' but as not sufficiently 

 known to me to be admitted into the body of the work. I 

 regret to say that I must still leave it undescribed. T did not 

 detect it while the gathering was recent ; and in cases where 

 doubt exists, a diagnosis from a prepared slide is usually insuf- 

 ficient for the foundation of a species, or even the correct deter- 

 mination of the generic position of a Diatomaceous frustule. 

 The same gathering furnished specimens of the rare British 

 forms, Nitzschia spathulata and Eucampia Zodiacus ; the latter 

 is however more general than its rare detection might seem to 

 imply, being only conspicuous in a fresh state, and becoming so 

 diaphanous when prepared in acid as to elude the notice of ob- 

 servers. Excellent specimens collected from a small pool on the 

 landing- slip at Birkenhead have lately been sent to me by 

 Mr. T. Comber of Liverpool, and the species is probably distri- 

 buted along most of the British shores. 



On the 19th June I reached Falaise and spent a few days 

 with M. de Brebisson, whose knowledge of algology, and more 

 especially of the freshwater forms of the Diatomacese, has so 

 often aided and illustrated my researches. 



It was unnecessary for me to explore a district that had for 

 years been subjected to the examination of so acute an observer, 

 and a rough gathering from the public fountain in the " Place,'' 

 graced with a noble statue of the Conqueror of England, was the 

 only one made in this neighbourhood ; it supplied a few common 

 British species, among which Gomphonema olivaceum was largely 

 predominant. 



On the 23rd July I proceeded by Alen9on and Le Mans to 

 Tours. The fearful inundations which had desolated the borders 

 of the Loire and its tributaries a few weeks before my arrival, 

 had borne off all accumulations of Diatomacese, and left little to 

 detain me in this otherwise rich and beautiful country. Pro- 

 ceeding rapidly to the south, I passed through Bordeaux to the 

 borders of the great salt lagoon lying a few miles to the south 



