42 H. B. POLLARD. 



dentary bones are separate, thus forming four independently moveable 

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



Weyenbergh 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 mastication, 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 w T ould 

 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. 1 Along with this is associated the 

 fact that the suspensorium possesses little mobility and the suspension 

 is little removed from autostylism, which I hold to be the primitive 

 condition. 



Of late years it has become customary to look upon the " Ganoids " 

 as derived from Selachii, while the Teleostei are regarded as a 

 flourishing offshoot from the least primitive of the Ganoids, Amia. 



When the Ganoids were established as a limited group by the weight 

 of Midler's authority, and further when the primitiveness of Selachii 

 was so strongly insisted on by Gegenbaur, it was but logical to 

 assume that a Selachian form gave rise to a Ganoid, and this in turn 

 to a Teleostean. 



However, the Ganoids are now being given up as a natural group. 



SagemehFs work illustrates the progress of such views. This author 

 directly compared Amia with Selachii, and came to the conclusion that 

 a form like Amia might be descended from an early Notidanus-\\k.Q 

 shark. Then he proceeded to show that the Gharacinidae are closely 

 allied to Amia, while a group including Siluroids, Gi/mnotidae, Ghara- 



1 This information I owe to my friend, Mr. E. T. Mellor, who has observed 

 the habits of Australian species. 



