256 Dr. Greville on some British Diatomacese. 



Cymbella lunata, W. Sm. PI. IX. fig. 5. Length -0013". 



Another new species, about the same size as the last, but the 

 strise are much stronger and more distant, and the shape nai'row 

 and elongated. The larger segment of the valve has a gentle 

 and equal curve, while the smaller segment is nearly straight, a 

 character sufficient of itself to distinguish it from the larger 

 C. Helvetica, which is ventricose. From C. Scotica it is sepa- 

 I'ated by the coarse striae and the obtuse ends. 



Navicula cocconeiformis, Greg. MS. PI. IX. fig. 6. 

 Length -0008" to -0011". 



Navicula nugax, W. Sm. MSS. 



A new species, somewhat similar in outline to Achnanthidium 

 fiexellum, with striae so fine that I have not succeeded in re- 

 solving them. I find that this species has been known for above 

 a year to Professor Gregory, who had both sketched and named 

 it previous to my detection of it in the Braemar gatherings. 

 He had obtained it from Elchies and various other places in 

 BanflFshire, and latterly from Loch Leven. 



Pinnularia hemiptera, Breb. 



This species, found, as Professor Smith informs me, not un- 

 frequently since the first volume of his work was published, I 

 met with almost pure near the Pass of Killiecrankie early last 

 summer. It was obtained by squeezing the moisture out of 

 SpJiagnum, and along with it occurred an undescribed species, 

 Pinnularia gracillima, Greg. ]\1SS. In the autumn I again 

 found it in the mountainous district of Redesdale in Northum- 

 berland, by resorting to the same process, and singular enough, 

 P. gracillima was there also, with scarcely any intermixture of 

 other diatoms. P. hemiptera greatly resembles P. viridis, but 

 is distinguished from it by the much finer striae, and pci-haps 

 also by a more strictly linear outline. It was scarce in the 

 Braemar gatherings, and unaccompanied by P. gracillima. 



Pinnularia late-striata, described by Professor Gregory from 

 the Mull deposit, and found recent by Professor Smith in Grass- 

 mere, is scattered through a number of the Braemar gatherings, 

 generally associated with other of the alpine Pinnularia, as P. 

 lata, P. alpina, P. divergens, &c. Though not plentiful any- 

 where, it seems to be generally diffused. Professor Gregory in- 

 forms me that it occurs in more than half of the very numerous 

 Scottish gatherings which he has examined. Professor Smith 

 likewise found it in Auver^ne. 



