502 MANUAL OF ZOOLOGY. 



blood to the heart by a distinct pulmonary vein, and in every 

 respect discharging the functions of the lungs of the higher 

 Vertebrates. It is true that the lungs of the Dipnoi are merely 

 a modification of the swim-bladder of the other fishes, but the 

 significance of the change of function is not affected by this. 

 Lastly, sometimes, at any rate, there are rudimentary external 

 branchiae placed on the side of the neck. This feature, as will 

 be seen shortly, is characteristic of all the Amphibians, either 

 permanently or in their immature state. 



Upon the whole, then, whilst for the purposes of systematic 

 classification the Dipnoi must be placed amongst the Fishes, 

 it is not to be forgotten that many of their characters are those 

 of a higher class, and that they may justly be looked upon as 

 a connecting link, or transitional group, between the two great 

 divisions of the Fishes and the Amphibians. 



As regards their distribution and mode of life, two species 

 at least of Lepidosiren are known the L. paradoxa from the 

 Amazon, and the L. (Protopterus) annectens from the Gambia. 

 They both inhabit the waters of marshy tracts, and are able in 

 the dry season to bury themselves in the mud, forming a kind 

 of chamber, in which they remain dormant till the return of the 

 rains. Recently there has been discovered in the rivers of 

 Queensland (Australia) a fish which has been described under 

 the name of Ceratodus Forsteri, and which shows itself to be 

 very closely related to the Lepidosiren. This singular fish (fig. 

 273) the "Jeevine"* of the natives is from three to six 



Fig. 273. Ceratodus Forsteri, the Australian Mud-fish, reduced in size. 



feet long, and has the body covered with large cycloid scales, 

 a species with smaller scales having been described as C. mio- 

 lepis. The skeleton is notochordal, all the bones remaining 

 permanently cartilaginous. There is a well-developed opercu- 

 lum, but as in Lepidosiren no branchiostegal rays. The 

 tail is homocercal, and the pectoral and ventral fins are sup- 

 ported by a median, many-jointed, cartilaginous rod, with 

 numerous lateral branches on each side. The heart consists 



* The name of "Barramunda " seems to have been given to Ceratodtis 

 by error, the native Australians apparently calling it the "Jeevine" or 

 "Teebine." 



