Fossil Foraminifera from the Cretaceous rocks of South India. Part I. Ariyalur area orbitoids

Abstract

The author is now engaged in a detailed study of the fossil Foraminifera from the Cretaceous rocks of South India; the present paper deals with the Orbitoids found in a limestone band recently noticed near Ariyalur, in the Trichinopoly area. The abundance of these Orbitoids, together with plenty of associated Siderolites, indicates that the containing rock is of Maestrichtian age and occupies a stratigraphical position in the Ariyalur group just below the overlying Niniyur Group (Danian). While some of the Orbitoids occurring here resemble certain species of Lepidorbitoides and Orbitocyclina already described, there are others which appear to be new. The paper gives a general account of these Orbitoids, drawing special attention to some of their interesting features. The probable significance of these in the study of the family Orbitoididae is briefly discussed.