Auckland Institute. 467 
have to use its wings some time before it had reached its least possible 
velocity. Bearing this in mind, it was shown that a diminution in velocity 
of 11:6 feet a second could be compensated for by an increase of one degree 
in the angle at which the bird happened to be flying ; and that, therefore, it 
was extremely probable that the albatros used its air cells to enable it to 
slightly shift its centre of gravity with respect to the position of its wings, 
and so, with little muscular exertion, to alter the angle at which it was 
flying. The essayist concluded his able and instructive paper by stating 
that he did not pretend to have solved the problem connected with the flight 
of the albatros, but merely to have suggested a method of solving it. Experi- 
ments required to be made respecting the resistance offered by the front and 
under surface of the bird to different velocities of wind before any satis- 
factory conclusion eould be arrived at. 
A vote of thanks was tendered to Captain Hutton for the care and ability 
he had shown in the preparation of this paper. 
2. * Notes on Land and Fresh-water Shells collected in the Northern 
Part of the Province of Auckland, during the Month of April, 1868," by 
T. B. Gillies. 
ABSTRACT. 
After a few O remarks, the author observed that, at the native 
settlement of [Waitatiora] Whitiora, he had found a fine specimen of the 
Bulimus crawling across the path, which appeared to be the Bulimus antipo- 
darum, but differing from some hundreds of specimens that he had seen, in 
having two strongly developed bars or projections on the inner side of the outer 
lip. The presence of half-burnt shells, on peat, at Whang , from which the 
fern had been previously burnt off, afforded ample evidence that it had once 
been a favourite habitat of the Bulimus antipodarum. -A smaller shell, which 
he was inclined to set down as the young of the Bulimus antipodarum, or an 
Achatina, had been obtained from the natives. None of the larger Bulimus 
antipodarum had been found at Bream Head, though abundance of the 
smaller kind were met with. However, he had some doubt of the identity 
of the Whangaruru with the Bream Head species. On Mania Hill, near 
Whangarei, he had found what at first sight appeared to be three varieties 
of a whorled shell, like a Turritella, but which he supposed to be a 
Cyclostoma. The larger variety had six whorls, about half an inch long by 
one-eighth of an inch in width, and of a brownish colour, indistinctly 
striped; the mouth being nearly circular and much contorted to the right, 
with a sort of double lip all round. The smaller variety, five whorls, a 
quarter of an inch to three-eighths of an inch long, had not the contorted 
mouth nor the double lip. The smaller variety was only ten-twelfths of an 
inch in length, by ‘7 in. wide. He had also obtained a large number of 
