M 



YORKSHIRE DIATOMS IN 1905. 



R. H. PHILIP. 



At two of the excursions of the Yorkshire Naturalists' Union 

 last year (Pocklinijton and Maltby) i^athering-s of Diatoms were 

 taken. The Givendale Springs, near Pocklington, yielded 

 almost pure gatherings of Diatoma hiemale, the only other 

 species present being that very fine form, Melosira arenana — a 

 truly lovely object under y^ oil immersion objective, owing to 



(b) 



A 



V 



1. Fra^ilaria capucina Desni. Type form, (n) Three frustules conjoined. (6) Valve 

 view. 2. Fragilaria capucina. Vax.mesolepta. Valve. 3. Pragilaria capucina. New(?) 

 variety from Roche Abbey Lake, (a) Valve, (b) Two frustules conjoined. 



its iridi.scent colours and delicate cross striation. The Ouse- 

 thorpe brook yielded a greater variety, of which the most 

 interesting form was a diminutive Diatoma elongatiim var. 

 tenuis in abundance. The other species present were : — 



Achnanthcs linearis W. Sm. 

 Diatoma hiewale (hyni^.) Heb. 

 Frairilaria virescois Ralfs. 

 Gonifihonenia montanum Schiiin. 



,, olivaceum Kiitz. 



,, parviilum Kiitz. 



Navicula gracilis Ehr. 



,, radiosa Kutz. 

 Siirirella ormlis Brob. 

 Syncdra ulna Ehr. 



,, Vaiichcria' Kutz. 



Vanheurckia %<ulga ris(TUw .) \'. H. 



The Maltby excursion was specially interesting from the 

 opportunity afforded of comparison of the gatherings taken 



Naturalist, 



