Art. V. — New or Little-knoivn Victorian Fossils in the 

 National Museum. 



Part II. — Some Silurian Molluscoidea. 



By FREDERICK CHAPMAN, A.L.S., &c., 

 National Musetun. 



(With Plates X., XL, and XII.). 



[Bead 14th May, 1903]. 



Certain of the species herein described as new forms undoubt- 

 edly show a more or less close relationship to well-known 

 European and North American types, both as to their general 

 features and superficial ornament. The Victorian examples are 

 here regarded as distinct only when they exhibit constant and 

 well-marked, though often minute, characters of their own. At 

 the same time it is our aim to point out their relationships, in 

 order that the homotaxial affinities between the southern and 

 northern forms may be kept in view. It should be remembered, 

 however, that the value of a correlation between limited horizons 

 in widely separated areas is liable to be unduly overestimated, 

 since we have conclusive proof afforded us, by the detailed study 

 of certain groups of Australasian fossils, as the Graptolites and 

 the Glossopteris flora, that formations which appear distinct in the 

 southern area include fossils which in the northern hemisphere, 

 and especially in Europe, would be regarded as representing a 

 mixed fauna or flora. In other words certain types of fossils 

 occurring in older or younger formations in Eui'ope or India, 

 may, in Australia be associated together in the same strati- 

 graphical series.^ 



The species now under description fall into one or other of the 

 two series of the Silurian, as defined by Professor J. W. Gregory,* 



1 For a further discussion on this subject see T. S. Hall's Presidential Address, Section 

 C, Austral. Assoc. Adv. Sci., Hobart Meeting, 1901, p. 165. 



2 J. W. Gregory: "The Heathcotian," Proc. Roy. Soc. Victoria, n.s., vol. xv., pt. ii., pp. 

 170-3. 



