W. M. BALE ON SOME OF THE DISCOID DIATOMS. 29 



Rattray, who has unaccountably assigned the name to an entirely 

 different form, while describing the true A. Ehrenbergii as 

 A. moniliformis Ralfs. A. Ehrenbergii was described by Ralfs 

 from his own knowledge, while A. moniliformis was merely a 

 name given by him to certain forms from Oran and Virginia, 

 which he had not seen, but which he judged from Ehrenberg's 

 tigures to be distinct, the distinction consisting in the division 

 of A. Ehrenbergii into compartments by double lines, while 

 A. moniliformis was divided by single ones. There is really no 

 difference, except such as depends on the size of the valves and 

 the number of the fasciculi. In small valves, containing few 

 fascicles, the interfasciculate rays form a wide angle with the 

 other series, and are therefore very marked ; and these are the 

 " single series of dots " referred to by Ralfs. In large valves 

 the fascicles are numerous and narrow, so the interfasciculate 

 rays form a small angle with the other series, which, stopping 

 short at various points, leave a double row of subulate blank 

 spaces along the sides of each primary or interfasciculate ray, 

 and 'these subulate areas constitute the "double lines" of Ralfs. 

 That the small valves from Oran and Virginia, and the large 

 ones from Cuxhaven, etc., are one and the same species is fully 

 recognised, however, by Rattray, but he names them A. monili- 

 formis. To any one who reads carefully Ralfs' account of 

 A. Ehrenbergii there can be no possible doubt as to the identity 

 of the species. It was established specially to include the 

 many-rayed forms described by Ehrenberg, which mostly occur 

 at Cuxhaven ; Ralfs also states that it is " very fine in Ichaboe 

 guano," and that most of the forms can be obtained therein ; 

 and further, that it is " common, both recent and fossil." One 

 species, and only one, answers perfectly to this description, 

 namely, that which Rattray calls A. moniliformis, but which, 

 in its larger forms, at least, has been recognised by observers 

 generally as A. Ehrenbergii. Rattray might have been justified 

 in preferring the name of A. moniliformis on the ground of 

 priority, but he has failed to perceive that the forms which he 

 has placed under it are no other than the A. Ehrenbergii of 

 authors, and has inexplicably assigned the name A. Ehrenbergii 

 to a species (or variety) differing entirely from that described 

 by Ralfs. It is not found at Cuxhaven, nor, so far as is known, 

 in Europe at all ; it is far from being common, either recent 



