THE DIPNOI. 



145 



Ganoids, the Teleostei are not known before the Cretaceous 

 epoch, when both Physostomi and Acanthopteri make their 

 appearance, under forms, some of which (e. g., Beryx) are 

 generically identical with fish living at the present day. 



VI. The Dipnoi.— The " Mudfishes " of the rivers of the 

 east and west coasts of Africa and of eastern South America 

 are nearly transitional forms between the Pisces and the Am- 

 phibia. 



The eel-like body, covered with overlapping cycloid scales, 

 tapers to a point at its caudal extremity, and is provided with 

 two pairs of long, ribbon-like, pointed extremities, and with a 

 caudal fin. 



Fio. 51.— TLo Mudfish {Lepidosirm). 



Mrz 



Fm. 52. — Skull ot Lepidosiren annectens : A, the oarieto-frontal bone; J5, the supra-orbi- 

 tal ; C, the nasal ; D, the palato-pterygoid ; E, tne vomerme teetn ; E^ {?., the ex-occipi- 

 tal ; Mn, the mandible ; Hy, the hyoid ; Br\ the branchiostegal rays ; Op^ the opei-euJaJr 

 plate ; cc, the parasphenoid ; y, the pharyngo-branchial ; (?/•, the orbit ; Au^ the auditory 

 chamber ; ^, the nasal sac 



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