2694 THE LUNGFISHES AND CHIM^EROIDS 



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 accompanying figure. 

 The lungfishes 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 LUNGFISHES Family LEPIDOSIRENID^E 



The three existing genera of lungfishes may be taken as the typical represent- 

 atives of an order including several extinct families, and known as the Sirenoidea. 

 Its essential characteristics are that the head is covered with membrane bones; that 

 the main dentition takes the form of large grinding plates, situated on the ptery- 



UPPER PALATAL TEETH OF AN EXTINCT I.UNGFISH (Ceratodus}. 

 (From Teller.) 



goid 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. 



For a great number of years there were known from the Triassic 

 ' ia " strata of various parts of Europe fish teeth 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 Cerato- 

 dus was suggested for the otherwise unknown fishes to which they pertained. Sim- 

 ilar 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 



