[Proc. Roy. Soc. Victoria, 23 (N.S.), Pt. II., 1911]. 



Akt. XXXIII. — A Revision of the Species of LiTiiojysis 

 in the Tertiary Beds of Southern Australia. 



By FREDERICK CHAPMAN, A.L.S., *fec. 

 Palaeontolo.^'ist to the National Museum. Melbourne. 



(With Plates LXXXIII.-LXXXV.). 

 [Eead 8th December, 1910]. 



Introduction. 



In the course of preparing a Catalogue of Type Fossils in the 

 National Museum, some difficulties arose with regard to the 

 names of our fossil species of the genus Limopsis. The separa- 

 tion of species in this genus is somewhat intricate on account 

 of the closely graduated characters of some of the forms, al- 

 though they can generally be grouped around certain central 

 types. Furthermore, the genus seems to have been remarkably 

 susceptible to any slight differences in the local surroundings, 

 and to the nature of the sediments which were laid down in the 

 various habitats. The evidence gathered from a consecutive 

 study of the range and variation of species of this genus 

 throughout the Victorian Tertiaries tends to show that the Ter- 

 tiary sedimentation in this part of the world was rapid 

 and continuous from the ba.se to the summit, In other 

 words, the species to which our fossil examples pertain are, 

 generally speaking, persistent almost throughout the series • 

 and in two important cases there are no palaeontological gaps 

 occurring which allow the appearance from foreign sources of 

 any forms distinct in shape or ornament, our species being 

 traced from point to point in all their gradations. 



Undoubtedly the central type-form of the genus is closely 

 iillied to that which Sir F. McCoy identified with the commonest 



134 



