542* CORRIGENDA. 



reader also, that the names and descriptions of figs. 90 and 91, A. Gomplecca, and A. fasciata, 

 have by some mistake been transposed, as stated in the errata, which I did not discover till 

 it was too late to correct it. Whether A. fasciata, fig. 91, shall also prove a form of A. 

 Grevilliana, for which I gave it in my last paper on the Glenshira Sand, I cannot at present 

 determine. 



5. The form represented in fig. 74 d, Plate XII., is, as I am now quite satisfied, entirely 

 distinct from Amphora laivis, and must be hereafter described as a new species. 



6. I have been able to introduce, at fig. 68 c, Plate XII., a figure of the remarkable 

 detached valve of Amphora ventricosa, which resembles a very slender Cymbella, and 

 occurs even longer and narrower than in the figure. In one dredging, I find it tolerably 

 frequent. 



7. In the disc of Coscinodiscus centralis, Ehr., as represented in fig. 49, Plate XI., the 

 central cells are shown considerably larger than is usually the case in the specimens which I 

 have of this Diatom. Indeed the cells, in the figure, are more like what is seen in the centre 

 of C. Asteromp>halus, Ehr., and the question arises, whether the specimen figured may not be- 

 long to the last-named species, or whether these two species may not, in reality, be essentially 

 one and the same. In a large number of specimens of C. centralis which I have lately 

 examined, the central cells are invariably but a little larger than the rest, so that the form 

 represented in fig. 49, if it be C. centralis, and I see no other difference, must have been, in 

 this respect, abnormal. I may add, that in these beautiful discs, some of which are consider- 

 ably larger than the one figured, the cells are distinctly arranged in spiral lines, as in engine- 

 turning, and as is seen also in C. radiatus. This character is but slightly indicated in the 

 figure. 



W. G. 



1st August 1857. 



