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LUNG-FISHES. 
mouth, after the manner of the higher Vertebrates. The membrane-bones covering 
the roof of the skull, which are very few in number, cannot be correlated with 
those of the bony fishes; their mode of arrangement being shown in the accom¬ 
panying figure. The lung-fishes are at the present day represented only by three 
genera, with but very few species, but they were formerly a very numerous group, 
which appears to have been on the wane since a very early epoch. 
The Existing Lung-Fishes. —Family Lepidosirenidje. 
The three existing genera of lung-fishes may be taken as the typical repre¬ 
sentatives of an order including several extinct families, and known as the 
Sirenoidea. Its essential characters are that the head is covered with membrane- 
bones; that the main dentition takes the form of large grinding plates, situated on 
upper palatal teeth of an extinct lung-fish ( Ceratodus ). (From Teller.) 
the pterygoid bones in the upper, and on the splenials in the lower jaw; that the 
body is covered externally with overlapping scales; that the notochord persists 
throughout life; that the paired fins are of the fringed type; and that none of the 
fins are armed with spines. The existing forms have but few membrane-bones to 
the skull; no premaxillse, maxillae, marginal teeth, or jugular plates; a fringed 
tail, furnished with a continuous vertical fin; and cycloid scales. 
Australian For a great number of years there were known from the Triassic 
Lung-Fish, strata of various parts of Europe fish-teetli of the remarkable type 
of the specimen represented in the accompanying figure ; and from the fancied 
resemblance to a deer’s antler, presented by these teeth, the name of Ceratodus was 
suggested for the otherwise unknown fishes to which they pertained. Similar 
teeth were subsequently obtained from Secondary rocks in India and also in South 
Africa, but it was not until the year 1870 that a fish was discovered in Queensland 
having teeth of a similar type. Known to the natives, in common with other large 
fresh-water species, by the name of barramundi, the Australian lung-fish ( C . forsteri) 
agrees so closely with the extinct forms that it is usually regarded as generically 
identical. Its mouth is furnished in front with a pair of chisel-like teeth situated 
on the vomers, behind which come a pair of palatal teeth of the type of the one 
shown in the figure, but carrying six complete ridges, and an incomplete seventh ; 
