1875.] part of the Dafl.it Hills, Assam. 41 



real increase ; the Giladeri nulla has cut into the alluvium and flows at its 

 very base, and, instead of the usual gradation of fall from terrace to terrace, 

 the whole thickness is seen at once and amounts to some 40 feet. The 

 high level of the Bisnath Plain is seen from here to extend on the north and 

 north- west by the tea-gardens of Diplonga and Dikro, and an isolated high 

 patch of alluvium occurs about 4 miles west of Sutia, gradually falling by 

 steps at long intervals into the present level of the land on both banks of the 

 Barowli. A series of accurate levels taken over this country would be most 

 interesting, but that it is of the same age as the clay plateau at Tezpur and 

 many other places in the Assam valley as far down as Gwalpara is certain. 

 It could only have been formed under very peculiar conditions, — in still water, 

 with the surface higher than it now is towards the delta, and with a far 

 larger water supply from the mountains ; gradual subsidence in the direc- 

 tion of the delta to the extent of a few feet and change of climate would 

 soon model such outliers of an alluvium probably coeval with the extension 

 of the Himalayan glaciers, the fine mud and sand from which would form 

 just such clays and sands as the plateaus are composed of. 



VIII. — Note on the molluscan Genera Coelostele, Benson and Francesia, 

 Paladilhe, and on some species of Land-shells from Aden. — By W. 

 T. Blanfoed, F. B. S., F. G. S. 



(Received June 24th ; — Read July 7th, 1875.) 



In the ' Annali del Museo Civico di Storia naturale di Genova' for 1872, 

 Vol. Ill, p. 5, is a description by Dr. A. Paladilhe of Francesia, a sup= 

 posed new genus of Asiatic mollusks. As the typical form of the genus 

 was found in India by Benson, a short notice of this paper may be useful 

 to Indian naturalists, the more so as there is, I think, good reason for 

 doubting whether the genus is really undescribed, and there are some 

 details in the paper in question, and in a subsequent one, containing de- 

 scriptions of some mollusca from Aden, which require correction. 



The genus Francesia was proposed by Dr. Paladilhe for a small species 

 found by M. Issel close to Aden, and recognised by its describer as 

 identical with a specimen from the banks of the Jumna sent to him by 

 Prof. Mousson. This Indian shell was received by Mousson from Benson 

 under the name of Carychium scalare. M. Paladilhe relates at length the 

 enquiries which he undertook in order to ascertain if this Carychium scalare 

 was described, and after consulting various authorities, amongst whom were 

 Messrs. Gwyn Jeffreys and Hanley, he concluded that it was not ; Mr, 

 6 



