Mr. R. M‘Andrew on Mr. Jeffreys’s last Dredging Report. 359 
there be searched for in vain in less than about 80 fathoms, 
are to be met with in much shallower water and greater fre- 
quency on the coasts of northern Norway. 
Myr. Jeffreys’s second proposition, that individuals and varie- 
ties are generally of smaller size when found in deep water, is 
confirmed by my own observation ; and I proceed to 
3. “The size of North-European specimens is usually 
greater than that of South-Huropean specimens of the same 
species,” —from which I must record my dissent, more especially 
if it is meant to be implied that size diminishes in proportion 
to southern latitude. 
The examples he names in support of his hypothesis do not 
bear it out, but might generally be quoted to prove (though 
there are many exceptions) what I conceive to be the true 
theory, viz. that species attain their largest dimensions under 
those latitudes and conditions, though not in the particular 
localities, most favourable to their numerical development ; 
and it is quite consistent with this proposition that certain 
species which find in high northern latitudes the circumstances 
most favourable to their existence and increase (Saxicava are- 
tica, Arca raridentata, and Chiton Hanleyi may be taken as 
instances) should attain smaller growth in more southern 
regions. 
Pecten septemradiatus I have dredged on the Scandinavian 
coast as far north as Finmark, without obtaining in its more 
5 
northern habitat a specimen so large as those of Loch F yne, or 
even larger than those of the Sicilian species (P. clavatus of 
Poli) which Mr. Jeffreys assumes to be identical with it. 
Pecten opercularis, Astarte sulcata, Artemis exoleta, A. lincta, 
and Natica Alderi all appear to attain their greatest dimen- 
sions in the British seas; but they are all distributed from the 
Mediterranean or coasts of Spain to those of Nordland or 
Finmark, and I have found them all as large in their more 
southern as in their more northern habitat. My specimens of 
Astarte sulcata from Gibraltar and from Finmark, the extremes 
of its range, are of equal size, and, in fact, not distinguishable 
one from the other. Léma hians L-have found largest : at Oban ; 
specimens from Nordland are similar to those from Loch Fyne. 
Mytilus adriaticus is, as far as my observation goes, smaller 
in more southern localities than in Britain; and I am not 
aware of its having been met with further north; but in my 
Dredging Report of 1856 I have given Britain as the locality 
of its principal development. The same observations will 
apply to Defrancia teres and Bulla utriculus as to Mytilus 
adriaticus, unless the former should prove to be identical with 
Pleurotoma boreale of Lovén. 
