44 BRITISH DIATOMACE.E. 



Dr. Balfour. Aberdeenshire, Dr. Dickie. Pass of Killiecrankie, Mr. 

 P. Grant. Ben Lawers, elev. 1 700 feet, Aug. 1855, Dr. Arnott. Perthshire, 

 Dr. Greville. 



I first detected this interesting species in gatherings made by Dr. Balfour 

 iu the above localities, and subsequently found it in collections of Dr. Dickie 

 and Mr. P. Grant, which have been in my possession for several years. Dr. 

 Arnott and Dr. Greville have since supplied me with specimens from other 

 localities, In every case the form is, however, very sparingly distributed 

 amongst other Diatomacece, and in no instance have I seen it in a fresh or 

 living state. In ignorance of its general habit and character, not even certain 

 to which subtribe it properly belongs, I am unable to determine its generic 

 position, and am obliged to place it with those species to which it most nearly 

 approaches in the structure of its frustule. These certainly are the species 

 included under the present genus, its frustules being annulate and definite, 

 and the septa opposite. Should a further acquaintance with the species in a 

 living state enable me to place it with confidence among those forms that 

 unite after self-division into a zigzag chain, I know of no character that would 

 separate it from Grammatophora. The absence of a curve in its septa, relied 

 upon by Dr. Greville, I cannot regard as of sufficient importance to constitute 

 a generic distinction, as this feature is scarcely noticeable in some states of 

 G. macilenta (see Plate LXI. 382), and is uniformly absent in G. stricta, 

 Ehr. (see Kutz. Bacill. xxix. 76). 



If, however, future observation require the separation of the present species 

 from the genus Grammatophora, I must at all events deprecate the adoption 

 of the name Diatomella, as contrary to a canon of nomenclature now, I 

 believe, generally received, viz. : — "Generic names are inadmissible that are 

 founded upon a resemblance to other genera, and which express this re- 

 semblance by diminutives, or by syllables, either prefixed or added." — 

 DeCandolle, The'orie Elem. Part III. 



Supp. Plate LXI. 383. 



Genus 44. TABELLARIA, Ehr. 



Frustules oblong, cohering into a zigzag chain, annulate ; septa alter- 

 nate, entire, direct ; valves linear, inflated at the centre and extre- 

 mities, striated. 



The annulate frustules and inflated valves distinguish the present 

 genus from Diatoma, and the alternate septa from Grammatophora. 

 Professor Kutzing has described three recent species of this genus, 

 finding a character for one of these in its opposite "vittae," and 

 distinguishing the other two by the circumstance of the one having 



