THE NAUTILUS. 65 



possible route 2 for the migration from America to Australia of these 

 Tertiary marsupials. But such a land could not have been con- 

 nected with New Zealand, or the marsupials would have wandered 

 there also. A great southward extension of Tertiary New Zealand, 

 considered probable by Sir J. Hector, 3 would, however, have availed 

 to people the latter with much of the fauna and flora of the suppo- 

 sitions Antarctic land, in the way that European plants are 

 believed to have reached the Azores. 



This theory of the origin of Australian marsupials would also 

 account for the discontinuous distribution of Gundlachia. 



The Australasian members of the genus known are G.petterdi 

 Johnston, G. beddomei Petterd, MS., and G. sp. undetermined, and 

 probably new, from Xew Zealand. 



At present G.petterdi appears to be known, as adult, from only 

 three localities : a small, shallow, stagnant pool near the First Basin, 

 South Esk River, Launceston, Tasmania (Johnston and Petterd); 

 a hill stream at Mt. Lofty, S. A. (Tate), and a chain of shallow, 

 stagnant ponds behind the sandhills at Henley Beach, near Ade- 

 laide, S. A. (Adcock, Pulleine and Hedley). In this latter locality 

 they were associated with Planorbis, Sulinus and Ancylua, the 

 latter only determined by the shell. Their habit was to cling 

 to drowned leaves and sticks, or to the submerged leaves and stems 

 of water plants. So closely do they resemble Ancylus that a careful 

 observer may, in the field, easily mistake one for another. 



The precise mode of the growth of the shell does not seem to have 

 been related by any writer. Johnston says (Proc. Roy. Soc. Tas- 



2 Had the alternative route advocated ("Island Life," 2nd ed. p 497) by 

 Wallace, "over what is now the Java Sea," been used by the marsupials, then 

 Timor and the South-Eastern Austro-Malayan Islands should, as Forbes log- 

 ically remarks, have preserved some remnants of the migrants amid surround- 

 ings so like Australia (Vol. iii, p. 22, Supplementary Papers, Royal Geo- 

 graphical Society, 1893). Spencer-has demonstrated (Rep. Aust. Assoc. Adv- 

 Sci., 1892, p. 118) "that the diprotodonts had their origin in the Euronotian 

 region," which also seems to me, though not to him, to indicate the south 

 rather than the north-west as the point of marsupial ingress into Australia. 

 In liis latest paper Prof. Zittel says (Geol. Mag., Nov , 1893, Vol. x, p. 512} : 

 " For its [i.e., Australia's] connection at one time with South America, the 

 abundant occurrence of fossil marsupials in the Santa-Cruz beds of Patagonia 

 is valid evidence." See also Lydekker, " Nature," May 5, 1892, Vol xlvi, 

 pp. 11-12. 



3 Address to the Geological Section of the Aust. Assoc. Adv. Sci , Adelaide, 

 1893. 



