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 
Jaber, 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, Zhynnus thynnus; the Horse Mackerel, Trachurus trachurus; the 
Skipjack of Australia, Zemnodon 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 Ray, 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, Sciwna antarctica, is thus 
regarded by some as differing in no essential points from the European Maigre, 
Scieena aquila. One of the Australian Mackerels, the Scomber anitarcticus of 
