74 



ritic traps* was ejected, was at about tlie incoming of existing 

 species. Sucli a deluge o£ igneous mass must have destroyed 

 terrestrial forms of life over the greater part of the southern 

 region of Victoria. A small portion of south-east South 

 Australia and part of Tasmania were involved in this catas- 

 trophe. From this it may be inferred, that the outlying 

 regions unaffected by the volcanic disturbances retained their 

 faunas and floras in all their pristine characters, whilst, on the 

 other hand A^ictoria was reduced to the condition of a tenant- 

 less tract, which was re-peopled by migration from surrounding 

 areas. A remnant of its more ancient flora and fauna was 

 doubtlessly preserved in the Grampians and other similar 

 mountain masses, which would seem to have been, in part at 

 least, beyond the reach of the volcanic eruptions. 



Into this organically new region immigration would take 

 place ; forms of limited means of dispersal would probably 

 undergo morphological change in transitu ; others with greater 

 inherent powers of locomotion, or those which were trans- 

 ported, nolens volens, with rapidity, may have continued 

 unaltered. Thus it may be conjectured that the endemic forms 

 are either remnants of an older fauna, or are modified from 

 extra-limital immigrants. Of the first, Helicarion atramentaria 

 may be cited, and of the latter, Helix exoptata. AVhilst Helix 

 hrevijoila may be mentioned as an example of an immigrant 

 form which has resisted modification. 



Touching the introduction of continental forms no special 

 difficulty exists, but in respect to that of the species common to 

 Tasmania and the continent the case is different. Such com- 

 munity of species implies a land connection, or at least a closer 

 proximity than what actually occurs at the present day. A 

 community of species is traceable as far back in geologic time 

 as the period of the formation of the Pleistocene sandrock 

 which fringes the southern coast line of Australia and the 

 islands in Bass Straits. The Pleistocene sandstone of Badger, 

 Barren, and other islands have yielded to the researches of Mr, 

 E. M. Johnston (Trans. Eoy. Soc. Tasmania for 1878, p. 41, et 

 seq.) the following living continental forms : — Helix pictilis^ 

 Succinea australis, Aplexa tenuistrlata, and JPomatlopsis striatula ; 

 the first of which occurs in similar deposits at Cape Xorthum- 

 berland. I have elsewhere (Trans. Eoy. Soc. S. Aust., vol. ii., 

 p. Ixviii.) pointed out that the Pleistocene sandstone was accu- 

 mulated wlien the land stood relatively higher than it does now, 

 and may thus have constituted a land connection between Tas- 

 mania and the continent, by way of which an interchange of 



* I consider the so-called porphyrites of Macedon, Dandenong, and other 

 high peaks to belong to the same geological series as the well-known basalts 



