VEETEBRATA. 



191 



Order IX. DIPNOI. 



DlPNEUSTI. SlRENOIDEI. PROTOPTERI. LEPIDOTA. 



Skeleton partially osseous. Gills free, a narrow gill-aperture 

 with a rudimentary gill -cover. Air-bladder double, lung-like. 

 Scales cycloid. 



Tbe notochord is persistent ; but the cranial bones are distinct. 

 In Lepidosiren the pectoral and pelvic fins are subulate and rnany- 

 jointed. There is a continuous vertical fin posteriorly. Eespiration 

 is effected by the lung, a modification of the air-bladder, as well as 

 by the gills. The heart has two auricles and one ventricle. The 

 lung is double in Protopteridae, single in Ceratodus. 



Lepidosiren paradoxa and another species inhabit the Amazon ; 

 Protopterus annectens the Gambia, Nile, &c. ; Ccratodus is from 

 Queensland. The two former genera are known as "mud-fish," 

 from the habit of burying themselves in the mud in the dry season. 



The Dipnoi are a suborder of Ganoidei for Giinther, while 

 they constitute a class for others. Claus divides them into two sub- 

 orders Dipneumona for Protopteridrc, and Monopneumoua for 

 Ceratodidse. Schmarda puts the Teleostei between this order 

 and the last. 



ProtopteridcB. 

 Lepidosiren. 

 Protopterus=Rhino- 

 cryptis. 



CcratodidcB. 

 Ceratodus (Bar- 

 ram unda. ) 



