PARENTAL CAEE AMONG FRESH-WATER FISHES. 413 



great group or subclass nanietl Crossoptervgians which were charac- 

 teristic or even predominant fishes of ancient times from the De- 

 vonian to the Jurassic j^eriod. One of the most striking external 

 features of the Crossoptervgians was the prolongation of the axes 

 of the paired fins and the consequent lateral or fringelike arrange- 

 ment of the rays along the axes. It is to this characteristic that the 

 name crossopterygian (or fringe-finned) alludes. 



During the same remote ])eriod in which the ancient Crossoptery- 

 giaus flourished lived also fishes so much like those forms that they 

 were confounded with them in the same group by so good a naturalist 

 as Huxley and by many others. They likewise had lobate paired 

 fins, but later it Avas found that instead of a distinct suspensorium 

 for the lower jaw there was no distinction between the suspensorial 

 elements and the cranium, and that all formed one piece with which 

 the loAver jaw directly articulated. There were no distinct npper 

 jawbones. The heart of the living representatives has the same kind 

 of antechamber as that of the Crossopterygians although otherwise 

 different. 



It Avas a long time before the facts thus epitomized became known 

 and appreciated. The histories of the ancient forms and the recent 

 ones were long told as those of beings entirely unrelated. That of 

 the living ones is as interesting as it is curious. 



Two very distinct families of Dipnoans are represented in the 

 modern world, one {Cerdtodontkis) confined to northern Australian 

 rivers and the other (Lejndosirenids) connnon to South America 

 and Africa. 



In 183C) a great naturalist-collector, Johann Natterer, discovered in 

 the Amazon basin an animal of Avhich he sent two specimens to the 

 Imperial Austrian Museum, and by the custodian of the museum 

 (Fitzinger) it was described as a reptile related to the Xorth Amer- 

 ican Si7'e7i and called Lepidosiren pantdoxus. Several years later 

 (1841) Thomas AVeir sent two specimens of another animal, taken 

 from the Gambia River, West Africa, to London. This species was 

 described by Owen and considered to be a true f><li related to the eels 

 and was at first called Protopteriis annectens, but later it Avas refei'red 

 by its describer to the same genus as the South American animal. 

 Owen thought the tw^o belonged to a peculiar " family " and made 

 " the nearest approach in the class of fishes to the Perennibranchiate 

 reptiles." In fact, none of the old authors had auA' real appreciation 

 of the relations of either animal. 



Quite a Avarfare Avas carried on for some time about the question 

 Avhether the animals Avere reptiles (ami)hibians) or fishes, but long 

 ago it was decided in favor of the piscine relationshi[) of the Lepido- 

 sirenids. 



