418 n B, POLLARD, 



Nor is there any reason, as far as distribution is concerned, for 

 denying to other families, such as the Clarima, an immense antiquity. 

 They are a now flourishing group, while the Dipnoi, with restricted 

 range are a decadent group. 



The dermal skeleton of IJypostoma and CaVichthys has been 

 exhaustively investigated by Hertwig, who found that their dermal 

 teeth are homologous with the placoid scales of Elasmobranchs. 

 Therefore the dermal skeleton must be regarded as exceedingly primi- 

 tive. From that of Hypostoma may be derived that of AcipenseVy 

 which however is considerably more modified. Recently Klaatscii 

 has attempted to upset Hertwig's conclusions, but I am not alone in 

 thinking that in spite of the technical excellency of Klaatsch's work, 

 he has signally failed to prove his point. 



Another feature of considerable interest is revealed by the oral 

 teeth of Hypostoniidae. Some forms have been excellently figured by 

 Kner. I would specially refer to his fig. 1, tab. 5. 



The bent hook-like teeth of the premaxillary and dentary bones 

 all converge in the same direction , and the two premaxillae and the 

 two dentary bones are separate, thus forming four independently move- 

 able blocks. Such teeth can only be used for hanging on to some object. 



Wetenbergii remarks "the fragility of these teeth is enough to 

 show that the fish cannot use much force with them, and this is not 

 necessary, because these fish feed on more or less putrescent organic 

 substances. I have met, for example, with many specimens round 

 a dead horse, which was decaying in the river Primero. It seems to 

 me that their mode of feeding does not deserve the name of masti- 

 cation, but rather of suction". It is of no little importance to find 

 that these archaic animals have a suctorial mouth. Possibly the 

 symphysial teeth of Coccosteus may also have been used for hanging 

 on. No doubt Coccosteus did not live on dead horses, but even in 

 palaeozoic times, there can have been no lack of decaying organic matter. 



Coccosteus also possessed normal teeth in its jaws , so that it 

 would appear to have been able, not only to hang on, but also to 

 bite in the usual fashion. 



The Siluroids are almost throughout characterised by having a 

 very small gape of the jaws. They will suck at bait and not swallow 

 it suddenly like ordinary fish'). Along with this is associated the 



1) This information I owe to my friend, Mr. E. T. TAklIjOh, who 

 has observed the habits ol Australian species. 



