47 



«ituated, the littoral, or shore-line inhabitants o£ the adjoining 

 seas have free access to migrate from north to south, and vice 

 versa, in such a manner as to follow the isothermal conditions of 

 their wonted habitat. 



Such accommodations, however, are not applicable in every 

 <3ase with regard to the inhabitants of the continents situated in 

 the southern hemisphere. It is true the marine fauna bordering 

 the shores of Southern Africa, America, and Australia have in 

 €ach case free access to migrate northwards in the event of the 

 isothermal conditions in the southern parts of these continents 

 getting colder. But so far as Africa and Australia are concerned, 

 at least, considering the great expanse and ocean depths that are 

 situated to the south of these countries, it is questionable if 

 the existing fauna were driven northwards by an increase of 

 €old, whether the breaches thus caused in the ranks of animal 

 life in these regions would be immediately replenished 

 by others indigenous to a colder habitat. "With regard to 

 Australia, Js^ew Zealand might be looked upon as being a 

 sort of halting place in the passage of marine life passing 

 between the frigid waters of the antarctic circle and those 

 of a more temperate character which encircle the southern 

 shores of Australia. But if the depth of sea be considered which 

 lies between the shores of Victoria and Xew Zealand, it be- 

 comes almost an impossibility that such a highway could have 

 been available for the migration of animal life during the time 

 of the last extreme glaciation. The resembling character exist- 

 ing between the non-fossiliferous clayey Miocene beds, also 

 the upland Miocenes, and the more recent deposits constituting 

 our seaboard plains, forcibly show that all were originated in a 

 similar manner. 



Since the foregoing was written I have revisited the grooved 

 a.nd striated rock surface at Black Point, Holdfast Bay, and 

 from what I then saw and could determine, the views as stated 

 in this paper regarding the phenomena w^ere fully substantiated. 

 On the top of the sea-cliff, where the surface of the bed-rock 

 has been exposed to the action of the north winds and that of 

 the sea for centuries, the grooved and striated rock-surface 

 rest, and consists of a bed of hard, slightly micaceous, schistoze 

 rock, occupying very nearly the anticlinal apex of one of those 

 minor folds of so frequent occurrence throughout the pre- 

 Silurian rocks of South Australia. The strike of the bed upon 

 which these interesting striations are impressed is in a parallel 

 direction with the furrowings, which are south- south-west by 

 north-north-east, and dip at an inclination of from six to eight 

 degrees to the west. Another peculiarity I observed on re- 

 visiting the scene of these striations (which, to my mind, have 



