398 DIATOM ACE^:. 



The species are all included by Ehrenberg in his genus 

 Gallionella. 



a. Filaments not globuliferous. 



* Extremities of the cells serrated at the edges. 



1. MELOSEIBA ARENOSA Moore, MS. 



Plate XCIII. Figs. 2, 3. 



Char. Filaments large, dark brown. Frustules * twice or even 

 three times broader than long, divided in the centre by a 

 double line. 



Gallionella variant Ehr., Die Infus. p. 167. t. 21. fig. 2. 

 Meloseira arenosa Moore, MS. M. arenaria Kails, 

 in Annals, vol. xii. p. 349. pi. ix. fig. 4. 

 Hal). On a wet bank near Larne, co. Antrim : Mr. Moore. 

 Inner extremity of the Giant's Causeway: Mr. W. 

 Thompson. Very sparingly in a stream near Shoreham, 

 Kent : Mr. Jenner. 



This is by far the finest species of the genus, and is evi- 

 dently the plant which Elirenberg had in view as the Melo- 

 seira varians of Agardh, his description of that plant being as 

 follows : 



" Corpusculis utrinque planis, cylindricis aut nummifor- 

 mibus, a dorso glabris, a latere radiatim striolatis, ovariis 

 flavis aut flavo-viridibus." 



It is probable, as Ehrenberg has correctly figured both 

 species, that he regarded the true Meloseira varians of Agardh 

 as the young state of his species. 



The end surfaces of the frustules are closely applied to each 

 other, faintly marked with radiating striae with their margins 

 serrated, the teeth of one frustule locking into those of the 

 other with which it is in contact, in the same manner as the 

 teeth of certain wheels arc made to fit each other. 



The name should be arenosa, and not arenaria. 



* The term frustule, applied to the Diatomacece, has the same meaning 

 as the word cell used to describe the Conferva. 



