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 Avhich 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 could 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. GilHes. 



Abstract. 



After a few introductory remarks, the author observed that, at the native 

 settlement of ["Waitatiora] Whitiora, he had found a fine specimen of the 

 JBuUmus crawling across the path, which appeared to be the BuUmiis 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 "Whangaruru, 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 do^vn as the young of the Bulimics antipodarum, or an 

 AcTiatina, 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 

 Gyclostoma. 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 



