4 Prof. W. Smith on the Diatomacese of the Pyrenees, 



Pic du Midi d'Ossau, collected a form new both to French and 

 English algologists, but which has been detected in the Tyrol by 

 A. Braun, and named by him Gomphogramma rupestre. It ap- 

 pears to be frequent in the Pyrenees, as I met with it in several 

 other localities. T have described it in its proper place. 



On the 10th of July I reached Cauterets, and during a stay of 

 three weeks in that mountain village had ample opportunities of 

 collecting the Diatomacefe of the neighbourhood. A few of these 

 will be found among my new species, but these are not so 

 numerous as I had anticipated. The characters of the Pyrenean 

 forms are only slightly modified from those of our own sub- 

 alpine districts, and the careful systematist is obliged to regard 

 such modifications as varieties rather than as new species. 



The hot sulphureous springs which abound in the vicinity of 

 Cauterets, although supplying " Barregene " in abundance, are 

 not prolific in Diatomacese. The latter enter but rarely, and 

 accidentally rather than substantially, into the composition of 

 this curious substance, which mainly consists of various species 

 of filamentous Algse, such as Oscillatoria, Leptothrix, and Phor- 

 midium. 



Three others of the Pyrenean valleys, those of the Gave de 

 Gavarnie, Gave de Bareges, and the Gave d^ Ad our, supplied me 

 with numerous gatherings, without adding materially to the 

 number or variety of the species collected at Cauterets. 



I left Bagneres de Bigorre on the 10th August, and reached 

 Paris on the 13th, having made but one gathering on the route, 

 from the fosse of the Chateau de Chambord near Blois, which 

 however proved wholly devoid of either novelty or interest. 



The gatherings made during the above excursion amounted 

 to sixty-four ; of these, nearly fifty contained species of more or 

 less interest in a geographical point of view, being many of them 

 identical with those collected on my former journey, and all of 

 them with forms found in the British Islands, and described in 

 the ' Synopsis of the British Diatomacese.^ 



I give a list of these, which I have divided into two classes. 



1st. Those collected in marine or brackish-water localities on 

 the western coasts of France. 



2nd. Pyrenean forms found at elevations varying from 3000 

 to 7000 feet above the level of the sea ; and I subjoin a list 

 of those species or varieties not figured or described in the 

 ' Synopsis/ 



In the first two lists I have annexed a cipher to the name of 

 the species, denoting the number of localities in which the form 

 occurred. 



