94 



Dipi 



loi — Sire)ioidei. 



Ischjodns in the Stonesfield Slate, and the latter genus ranges 

 upwards to the Uppei- Cretaceous. Nearly complete skeletons 

 have been f'cnind in the Lithographic Stone of Bavaria. Eda- 



Fio. r28. — Lower Jaw of Edaphodon lejHognathus, Ag. ; Middle Eocene, Bracklesham Bay, 



Sussex. 



phodon (Fig. 128) and Elasmodiis are Cretaceous and Eocene; 

 Ghimcera dates back at least to the Pliocene. 



Sub-class III.— DIPNOI. 



Wall-case, 

 No. 5, and 

 Table-case, 

 34. 



Order 1. — Sirenoidei. 



The typical Dipnoi (double-breathers) are so named because 

 in their living representatives the air-bladder assumes the 

 function of a lung, and thus furnishes them with a second 



KiG. 129.— Skeleton ot the African Mudfish, Pi-otopterus anne:ltiu, lining in the Rivers of 



Africa. 



means of respiration. They are a nearly extinct race, only 

 three forms now surviving, namely, Pivtopterus in Africa (Fig. 

 129), Lepldosiren in South America, and Geratodus (Epiceratodus) 

 in Australia (Fig. 130). 



Fig. 130. — "The Australian Mudfish," Ceratodas ForsUri (recent), Australia. 



The notochord in these fishes is always persistent, and the 

 tail is diphycercal or heterocercal. There are two pairs of 



