134 THE GREAT BARRIER REEF. 



distinction between the island and the continental individuals of those most interesting oviparous 

 monotremes, the Duck-billed Platypus, Ornithorhynchus anatiiuis, and the so-called Australian 

 Porcupine, Echidna, although in the last-named instance the colder climate of Tasmania has 

 evolved a finer-spined but more hirsute race, distinguished as E. aciilcata, var. sctosa, while the 

 remaining varieties are retained for the continental t3'pe. There are numerous other mammalia 

 whose representatives are generically, but not specifically, identical on the northern and on the 

 southern shores of Bass's Strait. These include the Wombat, represented in Tasmania by 

 Pltascolomys iirshius, and on the continent by two, if not three, distinct forms. The Rat- 

 and Jerboa-Kangaroos, genera Hypsiprymnus and Bettongia, while represented by single 

 species only in the island, number three or four distinct continental types. The fresh-water 

 fauna of Tasmania exhibits similar evidence of original continuity with the fauna of the 

 Australian continent. The so-called cucumber mullet of Tasmania, and Yarra herring of 

 Victoria, Proiotroctcs marcena, is a species nearly allied to the European grayling, common 

 to the rivers both of Tasmania and of Southern Australia ; and the same remark applies to the 

 almost unique fresh-water representative of the cod family, Gadopsis mannoratus, familiarly 

 known to colonists as the Blackfish. The largest known fresh-water crustacean, Astacopsis 

 Franklhn, a species of fresh-water crayfish, which grows to a weight of eight or ten pounds, 

 is confined to the northern rivers of Tasmania, its nearest ally on the mainland being a smaller 

 and more roughly spinous form, distinguished by the technical name of Astacopsis scrratus. 

 The Ringarooma district of Tasmania possesses a huge species of earthworm, Megascolidcs 

 tasmanicus, three or four feet long, and over an inch in diameter, which has a counter- 

 part on the Australian continent. The "early bird" to devour this worm is represented 

 on both sides of Bass's Strait by the Australian Ostrich, or Emeu, Dromceus novcc-hollandia'. 

 The Australian continent, as hereafter shown, produces vestiges of some still earlier birds, 

 evidences that shed a most interesting light on the question of the original junction of Australia 

 with other and yet more remote countries. 



The evidence as to the close alliance between the faunas of Tasmania and of the Australian 

 mainland is accepted by all geologists, as, in the case of New Guinea and of North Queens- 

 land, incontestable proof of a bygone continuity of the lands, and also of the present 

 combined area having subsided to at least the depth of the water in the intervening Strait. 

 Subsidence, as has been already shown, was contemporaneously progressing on the extreme 

 north of Australia, and it may be reasonably assumed that the same movement operated 

 throughout the eastern Australian seaboard. The reader, by referring to the accompanying 

 chart of the Barrier region, and elevating in imagination the sea bottom by forty fathoms (the 

 minimum depth of Bass's Strait) throughout the Great Barrier Inner Channel and reef area 

 generally, will arrive at results suggestive of the configuration of the land at the time of 

 the union of Australia and Tasmania. The Great Barrier, as a barrier, will be non-existent ; 



