3« 
THE NATURALISTS 7 JOURNAL. 
of communication with the Atlantic coasts of North America, 
or vice versa , and the shores of Greenland may be safely pointed 
out as that means of communication, although I may remark 
that certain petrels are able to maintain a flight across the open 
Atlantic, and frequently do so. As to the smaller land birds, 
some few species inhabiting Eastern North America are iden¬ 
tical with, and others only racially distinct from those of northern 
Europe, and the latter especially support the theory of the 
existence of a pre-historic communication with the European 
continent ; yet the vast majority of North American land-birds 
are entirely distinct from those of Europe, and in every way 
related to those of South America only. 
To return to my subject, it can be safety assumed that frail 
butterfly-life could not pass by means of the Arctic regions (at 
least, not under their present condition), and few, how¬ 
ever strong on the wing, could have accomplished a flight 
across the Atlantic.* So that probability points to some 
prehistoric means of communication—some Atlantis now 
lost beneath the ocean. It may be well to state that the 
alternative of introduction by the indirect agency of man 
is set aside by the obvious differences between European 
and American forms, which can only be the result of a long 
period of time. Still, it is extremely probable that the small 
white butterfly (. Pieris raped) has been so introduced. I met 
with this insect commonly in Nova-Scotia during the early 
spring, but was informed by my late friend Andrew Downs, 
(of Halifax, N.S.) that it was unknown there until within the 
last 20 years, and he considered that it had been introduced 
from England, 
THE EDITOR. 
{To be continued.) 
THE AUTOBIOGRAPHY OF A SWAN-MUSSEL, 
(A nodon ta cygnea .) 
{Concluded from page 17) 
“ The prismatic layer,” continued the Swan-mussel, “ consists 
of numberless polygonal prisms placed long edge to long edge,t 
and united by conchiolm. It is visible close to the margin inside 
the valves as a dark shagreened border, 
* The American species Danais archippus, which has of recent years reached 
our shores, has beyond doubt been introduced by means of some of the many 
vessels arriving heie. 
t Obliquely to the surface of the shell. 
