180 H. H. Godwin- Austen — Cyclostomacece offJie Dafla Kills. [AuGirsT, 



has been the immediate occasion of the jDresent imper. Mr. Buchan has 

 pointed out that the fall of pressm'e during the afternoon hours seems to 

 depend much on the local distribution of land and water as well as on the 

 position of the sun, the humidity of the air, and the direction of the wind, 

 particularly considered as a land or sea wind ; and that while numerous 

 illustrations could be adduced shewing a larger oscillation over the same 

 region with a high temperatm-e and a dry atmosphere, than with a low 

 temperature and a moist atmosphere there are some remarkable and striking 

 exceptions. One of them is presented by the Mediterranean on the 

 coasts of which sea, the amplitude of the oscillation is least, precisely at 

 that season when the air is driest. Mr. Blanford remarked that this ap- 

 parent anomaly is readily explained by the action abeady described. The 

 inequality of the dimnial pressures generated over land and sea will be 

 greatest when the sun's action is most direct ; when the solar rays, un- 

 impeded by cloud, fall on the land in the one case, on the water surface in 

 the other, and under such circumstances the transfer of air from land to 

 sea during the day will be a maximum, and the dim-nal fall of pressure on 

 the coast will be diminished by the local accumulation of air. 



It appears then in a high degree probable that a great part of the 

 diurnal irregularity of the barometric tides is due to the transfer of air 

 from land to sea and vice versa, and to a similar transfer which may be 

 proved to take place between the plains and the mountains. But the phe- 

 nomenon is very complex, and much study and labour are yet required to 

 unravel its elements, consisting as they do, partly of elastic and reactionary 

 pressure, partly of dynamic pressm'e, and partly of variations in the 

 static pressure of the atmosphere. Till this shall have been done, and it 

 shall be f otmd, after all, that heat and its effects are insufficient to exjilain 

 the phenomenon, it seems premature to resort to magnetic and electrical 

 phenomena for the explanation of the barometric tides. 



2. The Cyclostomacece of the Dafla Sills, Assam. — By Major H. H. 

 Godwin-Atjsten, F. E. G-. S., F. Z. S. 



The present list is confined to the operculated land shells and includes 

 33 species, of which eleven are described and figm-ed as new ; five were previ- 

 ously known from Dai'jiliug ; thirteen are well-known Khasi and Naga Hill 

 forms, and three or four extend to the Shan States. The Selicidce will 

 form the subject of a second paper, in which the author hopes to be joined 

 by Mr. G. Nevill. The most mteresting species described appears to be 

 Mega loviastoma tanyclieihis. 



The paper, which is illustrated by one plate, will be published in the 

 Journal Part II, No. 3, 1876. 



