1884-85.] 



Edinburgh Naturalists' Field Club. 



249 



the surface of the waters of the Firth of Forth.^ They inchule 

 specimens of — 



Surirella ovalis. 

 Thalassiotrix nitzschioides. 



C. Cryptoraphidie^. 



Coscinodiscus concinnus. 



II centralis. 



II radiatus. 



ti fimbriatus. 



II excentricus. 



II minor. 



II polyacanthiis. 



1 1 perforatus. 



Biddulphia aurita. 



1 1 gi'anulata. 



Auliscus sculptus. 

 Actinocyclus crassus. 



1 1 Ralfsii. 



Actinoptychus undulatus. 

 Hyalodiscus stelliger. 

 Chaetoceros boreale. 



II decipiens. 



II incurvuui. 



Melosira sulcata. 

 Syndendrium diadema. 

 Rhizosolenia styliformis. 

 Thalassiosira Nordenskioldii. 

 Cerataulus turgidus. 



Species of frondose forms, such as Schizonema Grrevilii, are not 

 uncommon in the tidal belt. They often occur attached to various 

 Algas, such as Polysiphonia? and Ceramia, and not unfrequently 

 bear other Diatoms on the sides of their muco-gelatinous filaments, 

 such as Synedra gracilis, Khipidophora elongata, Grammatophora 

 marina, Amphitetras antediluviana, &c. 



Various fresh-water species have also from time to time been 

 noted, among which may be mentioned the following : — 



A. Raphidie^e. 



Amphoi'a ovalis. 

 Cymbella scotica. 



11 helvetica. 

 Pleurosigma attenuatimi. 



11 lacustre. 



Navicula elliptica. 



Navicula amphisbrena. 



Gomphonema geminatum. 



II acuminatum. 



Cocconeis Thwaitesii. 



B. PSEUDORAPHIDIE.E. 



Epithemia gibba. 

 II turgida. 



^ The classification of Diatoms at present generally accepted is that liy 

 Professor H. L. Smith, and may be found in the ' Lens,' vol. i., 1872. It is 

 based on the character of the raphe on the siliceous valves. 



