254 Dr. Greville on some British Diatomacese. 



Odontidium Tabellaria, W. Sm. Diatomella Balfouriana, W. Sm., 



? Harrisonii, var. /3, W. Sm. nov. gen. 



Denticula tenuis, Kiitz. Tabellaria flocculosa {Roth). 



obtusa {Lyngh.). fenestrata (Lyngb.). 



sinuata, W. Sm. Melosira nivalis, W. Sm. 



Fragilaria virescens, Ralfs. distans, Kiitz. 



Achnanthidium flexellum, Breb. Orthosira spinosa, W. Sra., nov. sp. 



laneeolatum, Breb. orichaleea {Mert.). 



Diatoma tenue {Ag.). 



I shall now proceed to notice the new species and a few others 

 of novelty or rarity. 



Eunotia Camelus, Ehr. ? PI. IX. fig. 1. Length -0009". 



This is recorded in Kiitzing's ^ Species Algarum/ published 

 in 1849, as a native of the two widely separated localities, Cay- 

 enne and Labrador. It occurred in a recent state in one of the 

 Braemar gatherings, and has been observed by Professor Gre- 

 gory in others from Carr Bridge and Ben Nevis, and by Professor 

 Walker-Arnott in one from Fell End, Lancashire. I have like- 

 wise seen it fossil, but very rarely, in Lapland Bergmehl. This 

 diatom, in the opinion of the Rev. Professor Smith, is certainly 

 the E. Camelus of Ehrenberg and Kiitzing, notwithstanding the 

 inaccurate figure given by the latter, in which the base of the 

 frustule is represented as concave. In the form under consider- 

 ation the base is so remarkably straight, that it is difficult to con- 

 ceive how an artist could have made such an error in its deline- 

 ation. Professor Gregory, moreover, informs me that he has seen 

 in the Mull deposit a form exactly corresponding with Kiitzing's 

 figure; so that it is possible that two species may have been 

 confounded together. Under these circumstances I consider it 

 advisable to refer our diatom doubtfully to E. Cameltis, and to 

 add a figure for the guidance of the student. I have unfor- 

 tunately no access to Ehrenberg's illustration (Amer. t. 2). 



Eunotia tridentula, Ehr. PL IX. fig. 2. Length -0005". 



Found along with the preceding. It belongs to a little group 

 of minute, linear forms, quite distinct from the more robust and 

 convex series having the same number of undulations. The only 

 station given by Kiitzing for this species is America. Dr. Gre- 

 gory has observed it in a great variety of gatherings from Banff- 

 shire ; Carr Bridge, Morayshire ; from the Findhorn and from 

 Ben Nevis. Professor Smith obtained it also last year at a high 

 elevation in Auvergne. It is probably therefore of general dis- 

 tribution. 



Eunotia quaternaria, Ehr. PL IX. fig. 3. Length -0007". 

 A species scarcely to be distinguished from the last, except by 



