BRITISH DIATOMACEiE. 85 



Genus 29. LICMOPHORA, Ag. 



Frustules cuneate, stipitate ; stipes incrassate, irregularly branched ; 

 valves convex, elongated, inflected at larger extremity, and traversed 

 by a longitudinal median line. 



The frustules of the present genus differ in no essential respect 

 from those of UMpidopliora. They are, it is true, longer and narrower, 

 and probably less firmly siliceous ; but none of these circumstances 

 seem to be of generic importance. The separation of the genera must 

 therefore rest upon the fan-like arrangement of the frustules, upon 

 the summit of an incrassate and irregularly dichotomous pedicel, 

 which occurs in Licunophora. This character is however of more im- 

 portance than might at first view appear, as it indicates a peculiarity 

 in the self-dividing process. In Rhipidophora paradoxa and elongata, 

 self-division is immediately followed by the separation of the half-new 

 frustules and a dichotomy in the filamentous stipes ; while in the pre- 

 sent genus the frustules remain for some time coherent, and continue 

 dividing and multiplying on the summit of the pedicel, which becomes 

 elongated and incrassated at each successive repetition of the process. 



A branching, or rather longitudinal rupture of the pedicel takes 

 place at irregular intervals, and the entire plant presents us with 

 more or less complete flabella on the summit of the branches, and 

 imperfect flabella or single frustules irregularly scattered throughout 

 the entire length of the pedicel. Rhipidophora Dalmatica possesses 

 the same character to a certain extent ; but the flabella are much 

 less perfect than in the present genus, while its pedicel is occasion- 

 ally so abbreviated as to ally it to Podosphenia. 



I have given, in accordance with the authority of my predecessors, 

 two species of the present genus ; but I am far from satisfied that 

 they are truly distinct; and I am disposed to believe that a wider 

 comparison of specimens will necessitate their union. The fronds 

 of both are parasitic upon the larger marine Algae, upon Zostera 

 marina, and upon various species of Zoophytes. 



1. Licmophora splendida, Grev. F. V. nearly linear, frequently 

 attenuate, and rounded at the upper extremity ; V. imperfectly 



