Reports and Proceedings — Geological Society of London. 373 



shells that inhabited the rivers of the north-western Indian frontier 

 in Lower Siwalik times, none are now represented in the surround- 

 ing country, five have completely died out, and two have either 

 migrated eastward or have survived to the east and disappeared 

 to the west of India." There is good evidence to show that the 

 mammals are certainly immigrants from the west ; and it would 

 therefore seem that there has been an eastward migration, both of 

 mammals and molluscs ; species characteristic of older beds in the 

 west occurring in newer beds in the east, and vice versa. There 

 is some little doubt as to the exact age of the Lower Siwaliks ; 

 Prof. Martin Duncan, from the study of the Echinoderms and Corals 

 of Sind, referrina: them to the Lower Pliocene. As marine faunas 

 are of more value in fixing the geological age of formations than 

 those of the land, it is not improbable that this view may be 

 correct ; and, bearing in mind the above-mentioned migration of 

 the land fauna, it will not be found altogether inharmonious with 

 the evidence afforded by the latter. 



In the physiographical section the peculiar sigmoid curvature of 

 the strike of the rocks is noticed ; and this has apparently taken 

 place without any fracture. Many of the streams (as in the Himalaya 

 and elsewhere) frequently run at right angles to the strike of the 

 rocks, and flow in narrow clefts directly through tall ridges of hard 

 rock, which are often on an anticlinal axis. As there are no signs 

 of dislocation, the explanation of this peculiarity seems to be that 

 the streams once flowed at a much higher level than at present, and 

 gradually cut deep channels in the subjacent rocks of varying 

 hardness, and that subsequent denudation has removed all these 

 rocks, with the exception of the cores of harder beds, which now 

 form ridges standing far above the level of the rocks of the country. 



The part devoted to economic geology is necessarily brief, as the 

 economic products are but small. Coal occurs in the Bolan Pass, 

 and between Quetta and Sibi, and elsewhere ; but, as far as is known, 

 the seams appear small and are not likely to be of any practical 

 importance. Petroleum is said to occur in the Mari Hills, but 

 probably in small quantities. Sulphur and gypsum are found locally. 



The memoir is illustrated with three excellent plates of Lower 

 Siwalik Mollusca; it also contains a sketch of a natural archway 

 through a ridge of Siwalik conglomerate in the Bugti Hills. 



Mr. Blanford and the Geological Survey are to be congratulated 

 on the accomplishment of so much good work in a very difficult 

 country ; and now that Mr. Blanford has returned permanently to 

 England, the zoological and geological world will hope to continue 

 to receive a supply of valuable memoirs from his fertile pen. 



ia:B:eos,TS JV.3^iD i=i?,ooEEnDii<rc3-s. 



Geological Society of London. 



L— June 11, 1884.— Prof. T. G. Bonney, D.Sc, F.K.S., President, 

 in the Chair. The following communications were read : — 



1. "The Eange of the Palaeozoic Eocks beneath Northampton." 

 By Henry John Eunsou, Esq., F.G.S. 



