62 MEMORANDA. 
“3. Three dredgings made at the same time by the Rev. 
Dr. Barclay, in Loch Fine, off Strachur, at depths of fifteen, 
twenty, and sixty fathoms, also in October last. 
“4. Three materials: forwarded to me in October by the 
Rey. Mr. Miles, of Glasgow, who was for some time on the 
Holy Island, in Lamlash Bay. 
“One of these was washed from the nests of the Lima 
hians, as I had reported the richness of the former. These 
last were from seven fathoms in Lamlash Bay. This mate- 
rial, dredged, I think, in June, was not so rich in Diatoms 
as Professor Allman’s, but yet contained many interesting 
forms. 
“The second was a coarse red sand, dredged off Invercloy, 
Arran, which was rather poor. 
“The third was a mass of Corallina officinalis, taken with 
the hand, in rocky pools, at Corregills, Arran, when the tide 
was low. ‘The Corallina, proved to have been a good 
Diatom trap, and yielded a material, not remarkable for the 
number of species, but rich in individuals, and these nearly 
all of interesting, rare, or new species. 
“| had thus eleven different materials, no two of which 
were exactly alike, although im all certain prevalent forms 
occurred. In each, on the other hand, some forms, few or 
many were peculiar, and their presence gave a distinct cha- 
racter. A careful study of the whole has yielded interesting 
results; and these it is the object of the present paper to 
state as briefly as may be consistent with accuracy. 
“The first observation is, that these waters contain a very 
large proportion of all the known and described marine 
forms belonging to Britain, including a good many which 
have hitherto been very rare; so scarce, indeed, in some 
instances, that few observers have seen them. I may specify 
the following as being by no means rare, several, indeed, 
being abundant in these materials: 
Coscinodiscus concinuus. Pleurosigma delicatulum. 
Eupodiseus crassus. Ks transversale. 
is Ralfsii. Surirella lata. 
‘s sculptus. Himantidium (?) Williamsoni. 
Campylodiseus Ralfsit. Amphiprora elegans. 
Horologium. Podosira Montagnei. 
Navicula Hennedyi. Orthosira marina. 
a Granulata, Bréb. Grammatophora macilenta. 
» _ Lyra, Ehr. Biddulphia Baileyi. 
Pleurosigma rigidum. a turgida. 
" obscurum. 
“The second observation which I made was, that, as I had 
