802 DR. J. MURIE ON THE ANATOMY OF OTARIA JUBATA. [Dec. 6, 
thus happens here with the large Owl, the Adjutant, and other spe- 
cies that fly singly or in small flocks: a few first appear like harbin- 
gers; these are soon joined by new comers in considerable numbers ; 
and before long they are in myriads. Inconceivable numbers of 
birds are, no doubt, continually passing over us unseen. It was once 
a matter of wonder to me that flocks of Swans should almost always 
appear flying past after a shower, even when none had been visible 
for a long time before, and when they must have come from great 
distances. But the simple reason soon occurred to me, that after 
rain a Swan may be visible at a vastly greater distance than during 
fair weather, the sun shining on its snow-white plumage against the 
dark background of a cloud rendering it very conspicuous. The 
fact of Swans being seen almost always after a rain is only a proof 
that they are almost always passing. Whenever we are visited by a 
great dust-storm, myriads of Gulls appear flying before it; this is 
invariably the case even when not a Gull has been visible for months. 
A dust-storm is always preceded by long drought, so that from the 
watercourses being all dry the Gulls could not well have subsisted 
in the region over which it passes. Yet in seasons of drought Gulls 
must be incessantly passing over us, visible only when driven toge- 
ther and forced towards the earth by the violence of the storm. 
The bird I allude to is the Black-headed Gull (Larus cirrhocephalus). 
In seasons when Grasshoppers abound very much, flocks of these 
birds also appear, often in such multitudes as to free entire districts 
from the devastating swarms of the hated insects. It is a fine sight, 
and a welcome one as well, to see a flight of these birds settle on the 
afflicted district ; at such times their mode of proceeding is often so 
regular, that a body of them well deserves the appellation of ‘an 
army of birds.’ They come down with a swift graceful flight, and 
settle on the earth with loud joyful cries, but do not abandon when 
the work of devouring has begun the order in which the flock was 
disposed. It often presents a front of several thousand feet, with a 
breadth of but sixty or eighty; all along this line of battle the ex- 
cited cries of the innumerabie birds produce a loud, incessant noise. 
Every bird is incessantly on the move—some skimming along the 
ground with half expanded wing, others pursuing the fugitives 
through the air; and all the time the hindmost birds are flying over 
the flock and alighting in the front ranks ; so that the whole body is 
steadily advancing, and leaving the earth over which it passes free 
from the pest. The Black-headed Gull is one of our most common 
birds, and has many very interesting habits; I hope before long to 
make it the subject of another letter. 
« T remain, Sir, 
«Truly vours, 
“W. H. Hupson.” 

Dr. J. Murie read the second part of his memoir on the Anatomy 
of the Sea-lion (Otaria jubata). The present portion treated of the 
skeleton and nervous system, vascular and respiratory organs, di- 
