[Pkoc. Eoy. Soc. Victoria, 29 (N.S.), Part II., 1917]. 



Art. X. — On tlie Frobable Environment of the Palaeozoic 

 Genus Hercynella in Victoria. 



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



(Palaeontologist to the National Museum, Melbourne^. 



[Read November 9th, 1916]. 



The recent discoveryi of the interesting gasteropod Hercynella, a 

 supposed pulmonate or air-breathing mollusc, in the newer Silurian 

 or Yeringian of the Upper Yarra district in Victoria, leads one to 

 enquire into its mode of living. This enquiry may be conducted on 

 two lines — viz., that of the natui-e of the sediment in which it occurs, 

 and the other, regarding the fauna with which it is associated. 



Before entering upon these questions, it will be well to consider 

 the views of Marjorie O'Connell on this subject2 in regard to the 

 species of Hercynella occurring in the Waterlime Group ( = Upper 

 Ludlow) of North Buffalo, U.S.A., at what seems to be an identical 

 horizon as the Victorian, so far as one can judge by associated 

 faunas. Miss O'Connell's note on the " Habitat of Hercynella " 

 (loc. cit. p. 100) is here given in full : — 



"The horizon in Bohemia in which the largest number of Hercy- 

 nellas has been found is F or Upper Monroan [Lower Devonian]. 

 Here they are associated Avith vast numbers of graptolites, and also 

 with sponges, trilobites and tentaculites. The fauna is undoubtedly 

 marine, and since it is well-preserved, and the Hercynellas are also 

 numerous and in good condition, there is no reason for questioning 

 the marine habitat of the species of Bohemia. Furthermore, the 

 shells are comparatively thick, showing no lack of carbonate of lime 

 for impregnation. The one specimen from the Monroe limestone of 

 Michigan likewise has good marine associates, though its macerated 

 condition and the fact that no other specimens have been found 

 would leave it an open question whether it was a true marine form 

 or merely one swept out to sea by land waters. The Hercynellas 

 which have been found in the Bertie waterlime, seem to indicate 

 conditions other than marine, for their shells are exceedingly thin, 

 as though available lime were not abundant in the water in which 

 they lived, and, moreover, their faunal associates are not typical 

 marine forms, there being only eurypterids, ceratiocarids and the 



1 Proc. Roy. Soc. Victoria, vol. xxix., (n.s.), pt. i., IDKj, p. 99, pi. v., figa. 47, 48. 



2 Bull. Buffalo Soc. Nat. Sci., vol. xi., No. 1, 1914. De»crii>tion of some New Siliiric Gasterc- 

 pods, pp. 93-101, 1 plate. 



