12 Mr. C. C. Babingtou on a new British Viola. 



17. Pleurosipna lacustre, n.fip. Valve lanceolate, much attenuated 

 towards the acute extremities : colour pale brown. Average 

 length of valve T ^y of an inch, greatest breadth of ditto yy 1 ^ q 

 of an inch. Longitudinal and transverse striae y j± ^ of an inch 

 apart (v. v.). 



In ponds and clear ditches near Lewes, 1851. 



Its freshwater habitat separates this species from P. Hippo- 

 campus ; its more slender outline, acute extremities, and delicate 

 strise from both the former species ; it is less common than either 

 of them. 



Plate II. fig. 14. Valve of P. lacustre. 



18. Pleurostgma Spencerii, mihi. Valve lanceolate, slightly at- 

 tenuated, obtuse ; flexure slight : colour very pale brown. 

 Average length of valve ^fo °f an mc b, greatest breadth of 

 ditto g (/o o of an inch. Strise y q no o °f an mcn a P ai 't i v - v -)- 



Navicula Spencerii, Bailey, Quekett on the Microscope, p. 440. pi. 9. 



Not uncommon in ditches, mixed with Oscillatoriece, near Lewes, 

 1850. Mr. C. Poulton, Reading! 



This minute species closely resembles a young specimen of P. 

 Hippocampus or P. attenuatum, and should probably not be se- 

 parated from the latter. I can find no difference between the 

 British and American specimens, except that those of the latter 

 in my possession are slightly larger. 



Plate II. fig. 15. Valve of P. Spencerii (British) ; fig. 16. ditto of an 

 American specimen. 



Landport Cottage, Lewes, Nov. 1851. 



Note. — Since the above was written, I have been informed by 

 Mr. Kingsley, that P. speciosum has been found by Mr. Topping 

 at Walton in Essex. 



II. — Notice of a new British Viola. By Charles C. Babington, 

 M.A., F.R.S.* 



It gives me much pleasure to have to record the discovery of 

 another violet to be added to the British flora, which I have re- 

 cently obtained from my friend Mr. A. G. More of Trinity College, 

 Cambridge. He gathered it in June 1851 on peaty ground in 

 Garry Land Wood near Gort, co. Galway. 



It is only recently that we have learned, from the writings of 



* Read before the Botanical Society of Edinburgh, Dec. 11, 1851. 



