116 Professor Smith's Conspectus of the Diatomacese. 



but certain specimens of S.fastuosa are almost as round as many 

 Campy lodisci, and C. spiralis departs from a circular outline more 

 than most Surirellae ; whilst in a gathering in my possession from 

 Fish Spring, Salt Lake Desert, Utah, an apparent variety of 8. 

 striatula is as much twisted as a Campy lodiscus. Again, Amphi- 

 tetras and Triceratium are both combined with Biddulphia. The 

 latter grows in long zigzag chains ; I am not aware that the former 

 does so, having never studied it in the living state, but I fancy not ; 

 but at all events Professor Smith takes no cognizance of this difference 

 as to method of growth, attaching no importance to it. Biddulphia 

 has two processes, Triceratium three or more ; that, therefore, 

 appears no valid reason why they should be separated. Biddulphia 

 has usually a few spines, but so has Triceratium armatum. As 

 a general rule, Triceratium is seen in its side, and Biddulphia in 

 its front view, when the diatoms, of course, appear very different ; 

 but a front view of an entire frustule of Triceratium is remarkably 

 like a Biddulphia, and in a slide of selected diatoms from Singapore 

 which I have, containing entire frustules of Biddulphia reticu- 

 lata and Triceratium armatum, these forms would doubtless be 

 considered closely-allied species instead of distinct genera by anyone 

 but an experienced diatomist. Of course, the same arguments 

 would apply to Amphitetras, so perhaps the Professor may be right 

 in abolishing even these old and well-known genera. 



In the second portion of the Conspectus, in a sort of preface, 

 the author enunciates his ideas as to the structure of the diato- 

 maceous frustulse, following out the hints of Mr. Carter in the 

 ' Annals and Magazine of Natural History,' March, 1865, but 

 which are much more fully worked out by Dr. T. D. M'Donald in 

 the January number, 1869, of the same journal, and which it 

 would seem has escaped his attention. 



A Table of Species is promised hereafter, without which the 

 present Conspectus would be not only incomplete, but almost use- 

 less. Such a Table will involve not only a vast amount of labour 

 and trouble, but will require an intimate knowledge of every form. 

 Though many so-called species may be treated as mere varieties, 

 the Professor will scarcely be able to use his pruning knife as 

 trenchantly as he has done with the genera, and in the case of his 

 present enlarged genera of Biddulphia and Surirella, it is to be 

 feared that their number will be legion. 



It is scarcely to be expected that old diatomists, though they 

 may perhaps agree as to the propriety of the proposed changes, will 

 adopt them, as this would involve the renaming most of their speci- 

 mens, and the learning a new grammar, as it were, for their favourite 

 science ; but the Conspectus will probably be a boon to the rising 

 generation of students. I must, however, again express my regret 

 that it has been based on a purely artificial instead of a natural 



