1884-85.] Edinburgh Naturalists Field Club. 



249 



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

 specimens of — 



A. Raphidie.e. 



Pleiirosigma strigosuni. 

 II balticum. 



II formosum. 



n fasciola. 



scutellum. 



aspera. 



distans. 



digitoradiata. 



interna pta. 



convexa. 



tumida. 



sti'iolata. 



vitrea. 



Cocconeis 

 Navicula 



Amphiprora 



B. PSEUDORAPHIDIE.E. 



Raphoneis amphiceros. 



II belgica. 



Rhabdonema minutum. 



11 arcuatum. 



Diatoma minimum. 



Nitzschia sigma. 



II constricta. 



II punctata. 



n closterium. 



Dimeregramma minus. 



Surirella ovali.s. 

 Thalassiotrix uitzschioides. 



C. Ckyptoraphidie-B. 



Coscinodiscus concinnus. 



11 centralis. 



II radiatus. 



II fimbriatus. 



11 excentricus. 



n minor. 



II polyacanthus. 



II perforatus. 



Biddulphia aurita. 



IT granulata. 



Auliscus sculptus. 

 Actinocyclus crassus. 



1 1 Ralfsii. 



Actinoptychus undulatus. 

 Hyalodiscus stelliger. 

 Chsetoceros boreale. 



1 1 decipiens. 



It incurvum. 



Melosira sulcata. 

 Syndendrium diadema. 

 Rhizosolenia stj'liformis. 

 Thalassiosira Nordenskicildii. 

 Cerataulus turgidus. 



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

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

 Algas, such as PolysiplioniaB and Ceramia, and not unfrequently 

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

 such as Synedra gracilis, Rhipidophora 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. 



Amphora ovalis. 

 Cymbella scotica. 



II helvetica. 

 Pleurosigma attenuatum. 



II lacustre. 



Navicula elliptica. 



Navicula amphisbjena. 



Gomphonema geminatuin. 



II acuminatum. 



Cocconeis Thwaitesii. 



B. PSEUDORAPHIDIE.E. 



Epithemia gibba. 

 II turgida. 



1 The classification of Diatoms at present generally accepted is that by 

 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. 



