II.—A Contribution to the Molluscan Fauna of the Laki and Basal Khirthar Groups of the Indian Eocene

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Abstract
The Tertiary geology of north-western India is of particular interest on account of the extensive development of richly fossiliferous rocks of Lower Eocene (including Palæocene) age. The monographs by Cossmann and Pissarro (1909a, 1927) and Vredenburg (1928) have familiarised us with the well-preserved molluscan fauna of the Upper Ranikot beds (Palæocene) of Sind, while Lt.-Col. L. M. Davies' collection of mollusca from a slightly lower horizon in the Samana Range, on the North-West Frontier, has recently been described by myself (1930). With the exception, however, of one family, the Gisortiidæ, dealt with by Vredenburg (1927) and Schilder (1930), the mollusea of the overlying Laki group (Ypresian), as well as of the Khirthar group (Middle Eocene), have been neglected by modern workers. The well-known monograph by D'Archiac and Haime (1853–54), moreover, in which some Laki species are described, has always been a source of confusion owing to the fact that fossils from all horizons from the Danian to the Miocene are grouped together as “Nummulitic,” and no reliable information as to their respective horizons has been available.