154 THE NATURALIST IN AUSTRALIA. 



Continent, possesses a marked affinity, and even to a large extent identity, with the 

 species characteristic of the Indo-Malay region. The second one constitutes in itself a 

 highly characteristic south-temperate fish fauna which possesses many points of corre- 

 spondence with that of the littoral regions of both the North Atlantic and the 

 North Pacific. In some few instances, the correspondence of the types inhabiting 

 respectively these widely separated oceans is so remarkable that it has not been 

 found possible to associate them with independent specific diagnoses. It becomes 

 consequently incumbent to conclude that these in all recognisable respects 

 homoplastic types have been either arrived at by heterogeneous processes of evolution, 

 or that they represent one and the same species, whose members have become 

 widely separated as the result of some marked change in the relative positions 

 of, and intercommunicating currents between, the larger oceanic areas since their 

 earliest appearance under their existing specific forms. 



As examples of fish which are bracketed with a corresponding synonomy, and 

 occur as indistinguishable types in such remotely situated areas as the temperate 

 Australian and European seas, reference may be made to the John Dory, Zeus 

 faber, purchasable in either the London or Sydney markets ; the Sprat, Clupea 

 sprattus; the Conger Eel, Conger vulgaris; the Frost Fish of Australian and New 

 Zealand seas, Lepidopus caudatus, synonymous with the Scabbard Fish of European 

 seas ; -the Tunny, Thynnus thynnus ; the Horse Mackerel, Trachurus trachurus ; the 

 Skipjack of Australia, Temnodon saltator, known on the East Coast of North 

 America as the Blue-fish; and the little Bellows-fish, Centriscus scolopax. Many 

 species of Sharks and Rays, such as the Blue Shark, Carcharias glaucus; the 

 Porbeagle, Lamna cornubica ; the Fox Shark, Alopecias vulpes; the Spiny Dog-fish, 

 Acanthias vulgaris; the Angel-fish, Rhina squatina; and the Eagle Eay, Myliobatis 

 aquila, are also common to the European and Australian waters, but, as they are for 

 the most part ocean rovers with an almost cosmopolitan distribution, their presence in 

 these widely separated areas does not possess the same significance. 



In addition to the list just enumerated, a number of species might be 

 mentioned, concerning which, while they occupy such widely separated habitats, the 

 recognisable points of distinction are of so trifling a description that it is a matter 

 of dispute among ichthyological authorities whether they are to be regarded as 

 identical or independent species. The Australian Jew-fish, Scicena antarctica, is thus 

 regarded by some as differing in no essential points from the European Maigre, 

 Scicena aquila. One of the Australian Mackerels, the Scomber antarcticus of 



