2G0 Dr. Greville on some British Diatomacese. 



I am not aware of the original station. It is scattered through 

 two or tliree of the Braemar gatherings, and I found it near the 

 Pass of Kilhecrankie last summer. Professor Smith is, I believe, 

 under an impression that Coscinodiscus minor may turn out to 

 be the sporangial form of this species. 



Melosira distans, Kiitz. 



I was not aware of this diatom having been previously col- 

 lected in this country, until Professor Gregory recently informed 

 me that he had noticed it in a gathering from Elgin, as well as in 

 some other collections from the north of Scotland, but believing 

 that it was already known as a British species, he had not drawn 

 attention to it. The gathering placed in my hands is remarkably 

 pure, and agrees exactly with slides in my possession from Bilin 

 and Habichtswald, stations given by Kiitzing. Professor Smith 

 found it also in Auvergiie. It is much to be regretted that a 

 note of the precise locality of this diatom was not preserved, as 

 it is the only station for the rare Odontidium anomalum, which 

 was found intermixed with it. 



Orthosira spinosa, W. Sm. PI. IX. fig. 14-17. 

 Orthosh-a spinosa, W. Sm., Ann. of Nat. Hist. vol. xv. p. 8. pi. T. 



This is another instance of the all but simultaneous dis- 

 covery of a new species by Professor Smith in France, and Pro- 

 fessor Balfour in Scotland. It was collected by the former on 

 Mont Dore, at an elevation of 4236 feet; by the latter in a 

 locality where it would be produced under a corresponding tem- 

 perature, if we take into consideration the difference of latitude. 

 The structure of this plant is very interesting. The outer wall 

 of the cylindrical filament is continuous, but separates sponta- 

 neously at the junction of the valves, where the inner wall con- 

 tracts in a rounded manner. The valve is here beautifully 

 striated, the stri?e being coloured and semi-opake at the junc- 

 tion, but soon becoming colourless, and gradually disappearing 

 in the transparent tissue of the valve. When the orifice of the 

 valve is examined, it is found to be closed by a concave diaphragm 

 marked with radiating strise, coloured at the circumference and 

 pale and mouiliform as they approach the centre, where there 

 are usually three or four minute perforations. The peculiar 

 character of the species lies, according to Professor Smith, in 

 the valves or frustules being furnished at the point of junction 

 with a fringe of spine-like jorocesses; but I confess that I have 

 beeu unable to make out this character to my satisfaction. I 



