Cymbella.} KLGM DIATOMACE^E. 415 



Moist rocks and on the ground. Appin, Captain Carmichael. Pent- 

 land hills, Dr. Greville. — It forms a thin pale ochraceous stratum. 

 Frustula at first united in pairs, at length separated. Two globules are 

 sometimes present, which, in a dry state, seem to disappear, at least in 

 my specimens. 



4. C. reniformis, Ag. {kidney-shaped Cymbellci); " frustula 

 reniform adhering in pairs." Ag. Conspect. Crit. Diat. p. 10. 



On reeds, in ponds and streams, Mr. Arnott. — I am not certain 

 whether I am right in referring the plant before me to C. reniformis. The 

 frustula are hyaline and of a very pale yellow, and at length separate. 

 I have only seen it in the dry state. 



