ON THE FILAMENTOUS, LONG-HOKNED DIATOMACE^. 105 



On the Filamentous, Long-horned Diatomace^e, with a De- 

 scription of two new species. By Thomas Brightwell, F.L.S. 



In a o^athering of Diatomaceae, made by the late Mr. Wigham 

 in July 1854, on the borders of the salt-water estuary, called 

 Breydon, near Yarmouth, a singular filamentous, horned species 

 was detected, allied to the genus Chatoceros of Ehrenberg. 



An examination of this singular organism, (the first of the 

 family which has occurred in this country), and a comparison 

 of it with the allied forms described by Ehrenberg and Dr. 

 Bailey, afford materials calculated to extend and correct our 

 knowledge of this rather doubtful group of Diatomaceae. 

 Mr. Wigham's discovery will also, we trust, induce surviving 

 labourers in the same field, to endeavour to add to our know- 

 ledge of existing species, as much must yet be brought to 

 light before a satisfactory classification of this group can be 

 effected. 



Most of the described species have been found only in a 

 fossil, or rather, if we may so term it, a deposit state ; and in 

 this state it is clearly difficult to form a correct idea of either 

 species or genera, since deposits give no information as to the 

 Diatoms being in threads or solitary frustules. 



Fiom this circumstance, and a disposition to describe every 

 variety of form, and even many fragments of Diatoms, as 

 species, both species and genera have been multiplied to a 

 perplexing extent. It appears probable that there are few, if 

 any, instances of truly fossil Diatoms, but that all the so-called 

 fossil species are only deposits from still-existing and living 

 species ; and it is only wlien we have the living Diatom before 

 us, tliat we can give any specific or generic characters that 

 can be at all relied upon.* 



The discovery of a new and living species of Cliaitoceros., and 

 a careful examination of most of the species of this and seve- 

 ral other allied genera, described by Ehrenberg as found in a 

 fossil state, have satisfied us that most, if not all these, will, 

 when found in a living state, turn out to belong to the singu- 

 lar filamentous and horned group, which may for the present, 

 with some extension of its character (such as is hereafter 

 attempted in this paper), be comprehended in the genus 

 Chcetoccros. 



Tlie typical species of Ehrenberg's genus appears to be C. 



* In proof of this, Ehrenberg's genus Biblarum seems entirely composed 

 of the disjecta membra of several genera, as Tetracydus, Odontidium, and 

 some others. Tetracyclas emaniinatin^, Wm. Smith, {Bihlarum emargina- 

 tum, Ehr.,) has been found recently, in a living state, both in Ireland and 

 Scotland. 



