360 Mr. R. M‘Andrew on Mr. Jeffreys’s last Dredging Report. 
Of the distribution of Jsocordia cor our information is im- 
perfect. The Dublin-Bay specimens are, I believe, the largest. 
T have dredged it in at least two localities in the Hebrides, 
though only dead in an adult state, my largest examples much 
below the ordinary dimensions of the species. 
Tellina balaustina is of extreme rarity in the Atlantic, 
where next to nothing is known of its distribution. Except 
on our northern coasts, the only Atlantic specimen of which 
information has reached me is a single valve obtained by my- 
self, in company with the late Dr. 8. P. Woodward, off Cape 
Finisterre of Spain. In the Mediterranean the size I have 
found to vary, not from north to south, but from east to west, 
being smallest in the Augean and largest at Gibraltar ; so that 
this species does not throw any light upon the question. 
Tectura virginea is about as large in the Bay of Vigo as in 
the British seas, much larger than I have procured it from 
more northern latitudes on the Scandinavian coast. 
Of Defrancia purpurea my finest and largest specimens 
were obtained at Vigo. 
The foregoing examples (not selected by me, but by Mr. 
Jeffreys) render it, I conceive, needless for me to bring for- 
ward any instances in support of my views. I may, however, 
name a few of the commonest and best-known Mollusca of 
our shores, as Purpura lapillus, which I have found largest in 
the south of England, Mytilus edulis at Algiers, Buccinum 
undatum in Shetland (frequent in the neighbourhood of the 
North Cape, where it is much smaller), Fusus antiquus in 
Liverpool Bay, &c. 
T should not omit mention of two striking exceptions to 
what I conceive to be the general rule—viz. Haliotis tubercu- 
lata and Chiton cajetanus, both of which attain their largest 
dimensions in their most northern habitat, the Channel Islands 
and south coast of Brittany respectively. This I do not pretend 
to account for. They do not progressively augment im pro- 
portion to their northern latitude, as I have obtained both 
species on the north coast of Spain, where they are no larger 
than in the Mediterranean. Other southern species which 
find their northern limit on our coasts (e. g. Venus verrucosa, 
Cytherea chione, Cardiu maculeatum, and C. tuberculatum) are 
larger in the Mediterranean. I could cite a few exceptional 
instances of specimens being larger in their southern distribu- 
tion; but, to show that there are other conditions besides lati- 
tude which affect growth, I will mention that the individuals 
of Chiton fascicularis are uniformly larger at Mogador than I 
have found them elsewhere, while at no great distance, at 
Lancerote, they are much smaller than in any locality that I 
