362 SECTIONAL TRANSACTIONS.— C, D. 



dry basins or the oceans. Marine, lacustrine, and desert deposits as far 

 as they can be considered to be derived from the neighbouring land can 

 be said, according to the late W. Penck, to stand in a correlation with 

 processes which loosened their particles from the maternal rocks and 

 transported them to their present place of occurrence. Penck even tried 

 to make out correlation between deposits and land forms. This can, how- 

 ever, rarely be done reliably. Firstly, the preserved land forms are com- 

 paratively very young ; the oldest of them are hardly younger than upper 

 Tertiary. So the correlated sediments are, in a great part, still covered by 

 the sea. Then, the large series of little changed deposits of terrestrial 

 origin are correlated with times when erosion was rapidly going on in the 

 land which supplied the material. So the features of the landscape there 

 were changing rapidly and few of them could be preserved for any long 

 time. On the contrary, little inclined forms of an advanced planation can 

 be preserved much longer, or, at least, forms that succeed them on water 

 divides do not differ from the original ones so much. But these persistent 

 forms were modelled in a time when comparatively little material was 

 exported from the region and accumulated outside of it. Besides, the 

 sediments simultaneously laid down in the seas or lakes were exposed much 

 longer to marine and lacustrine influences and more changed by them. 



Sometimes valleys and other land forms filled with marine or lacustrine 

 deposits are shown by them to be not much older than these sediments ; 

 but rarely can a whole system of topographic features formed at the same 

 time be followed. In recent arid basins the chances to establish a correla- 

 tion of topographical features and deposits seems to be better than else- 

 where. 



Some examples of correlated sediments and processes, in some cases of 

 land forms also, form the Bohemian Massif, and the Alps are shortly 

 described. 



SECTION D.— ZOOLOGY. 



Thursday, September 2. 



Presidential Address by Prof. F. A. E. Crew on The sex ratio. 



Discussion on the Presidential Address (11.15). 



Mr. A. J. Marshall and Dr. J. R. Baker. — The sex ratio in the wild 

 animal populations of the New Hebrides. 



The sex ratio of most of the resident birds of the New Hebrides (Pacific 

 Ocean) is high. If all the species collected by the Oxford University 

 Expedition are lumped together, the percentage of males is 57 T i 'O. 

 More than fifty specimens were taken of each of twenty species, and among 

 these males predominated in seventeen. The highest percentage of males 

 was in the cuckoo, Cacomantis pyrrhophanus (82 T 5 -i) and in the honey- 

 eater, Myzomela cardinalis (80 T 3 '6). The sex ratio of nestlings approxi- 

 mates to equality. In the fruit-bat, Pteropiis geddiei, the males are 

 69 -F 3 '3 per cent, of the population. In the insectivorous bat, Miniopterus 

 austraUs, however, the sex ratio is almost equality (51 ^ 1-9 per cent, 

 males). It is suggested that sex ratio is generally a non-adaptive character, 



