1871.) AT 
we have at present, others now peculiar to that district only ; that this 
warmer period lasted for a time long after this is shewn, as instanced 
in that paper by specimens of a fresh-water shell, now found in the 
Nile only, being common in a semi-fossilized condition in land that was 
then, without doubt, covered by the sea. 
Examples of this group of migrants are indicated by an asterisk in 
Stainton’s “ Tineina of Southern Europe,” wherein are thus summed up 
the reasons of their peculiar distribution : “I believe most of these are 
“species which require to feed up as larve during the winter, and can- 
“not stand the prolonged severe cold of continental Europe.” Surely 
all this group must have been sadly thinned by the past season ! 
3. Direct migrants. 
The junction of England to the continent was probably on the 
eastern side, where the North Sea now rolls ; and, if the water drainings of 
Europe were conducted upon anything like its present plan, the British 
Channel must have been a vast estuary, leading to the mouth of 
the Rhine. Whilst England was thus part of the continent, there 
must have been a constant, steady migration, from the German 
side, of all the insects fitted to live in our island ; to these I have given 
the name of “ direct migrants,” and they constitute the large bulk of 
our Lepidoptera. A very happy illustration of each of the three classes 
here described is given in one genus of another order; Cordulia enea 
is a direct migrant, Cordulia arctica is an Alpine insect belonging to 
the glacial period, whilst Cordulia Curtisii affords a good example of a 
southern form, yet existing in the New Forest. 
The insects of Ireland have, so to speak, been filtered through Scot- 
land before reaching the Emerald Isle, the same applies also to the Isle 
of Man, yet this does not explain all the peculiarities of these two local- 
ities : a careful examination of the Lepidoptera of the Mull of Galloway, 
with a view to comparison, has not been made,—that is, at least, as far 
as is known to me. 
4. Western migrants. 
This group is doubtful; yet, from analogies in the distribution of 
plants, it is extremely probable that such exists. In plants there are 
many, the occurrence of which in England we can scarcely explain on any 
other theory. The distribution of Pinguicula lusitanica, Erica mediter- 
ranea, Ononis reclinata, and many others, almost requires such a supposi- 
tion. The very presence of such plants as Erica cinerea and Agraphis 
nutans, so rare in Germany, is suggestive of such a western migration ; 
on the other hand, it is fair to confess that in Connemara we find Naias 
