322 Dr. Dickie’s Notes of Diatomacese 
where, especially towards their outer extremities. It is the 
y:^jth of an inch in diameter. 
My specimen consists of at least three layers inclosing two 
inner cavities, which contain a green endochrome. In this it 
resembles many other allied forms. From what has appeared to 
be a single disc of Arachnoidiscus Japonicus, I have separated as 
many as six siliceous layers. 
This separation into laminse, marking the existence of so many 
individual frustules, reminds us of Meloseira and its allies ; — a 
resemblance that becomes the more striking, when we remember 
that as in Meloseira^ the fii’st frustules of Arachnoidiscus , Cocconeis 
and many others are attached, as parasites, to some other body. 
In the analytical table of the Bacillarice originally given by 
Ehrenberg he includes many of these objects ; classing Cocconeis, 
Actinocyclus, and what he calls Bacillaria, together in his group 
of Naviculacea, and characterizing them as free,^’ in contradi- 
stinction to his ^^fixed” forms, in which latter he includes Isthmia 
and other genera. It appears evident, however, that Cocconeis 
and Arachnoidiscus are as fixed ” when found in situ as any of 
the Diatomacece, and probably many of these other allied genera 
will eventually be found to exhibit the same feature when better 
known. I have elsewhere* * endeavoured to show the close rela- 
tionship which exists between these discs and the already recog- 
nized Diatomacece, and I cannot but think that by the time my 
enthusiastic friend Mr. Ralfs resumes his valuable labours upon 
the British species of this interesting group, he will find it ne- 
cessary to include in his classification a large portion of our native 
species of what are commonly called Siliceous Infusoria.” 
I would propose for the above species of Campylodiscus the 
name of C. horologium. 
Manchester, March 23, 1848. 
XXXIII. — Notes o/ Diatomacese /ownc? in the stomachs of certain 
Mollusca. By George Dickie, M.D., Lecturer on Botany in 
the University and King’s College of Aberdeen f. 
Professor E. Forbes has remarked that the stomachs of fishes 
are often zoological treasuries. The Haddock is a great concho- 
logist ; the Cod is more devoted to the Echinodermata, having a 
great taste for that tribe. 
Certain Mollusca are equally indefatigable collectors of Dia- 
tomacece ; they have been found in the stomachs of the Oyster, 
* Memoirs of the Manchester Literary and Philosophical Society, vol. viii. 
p. 48 et seq. 
t Read before the Botanical Society of Edinburgh, March 9, 1848. 
