420 H- ß- POLLARD, 



as far as can be seen, by no means of a low type. At the same 

 time there is nothing in the remains known to us which will indicate 

 even approximately their affinities to any one of the large groups 

 recognised in the classification of Aniphirhiue fishes." "The series of 

 scales or bones along the body of Cephalaspis —so strongly recalling 

 the cinctures of Calliclithys which has a complete endoskeleton — are, 

 probably, morphologically of the same nature as those structures, but 

 anteriorly I have not been able to detect any modification of the 

 flanking 'scales' in Cephalaspis in the form of clavicular bones." "It 

 is best then to let the group of Cephalaspidae stand alone." 



Pander, Huxley and Ray Lankester are therefore agreed that 

 the dermal aimature of Loricarina is like that of the oldest known 

 vertebrate fossils. 



Clatpole (1892) has discovered Crossopterygian fins along with 

 a Pteraspidian, Palaeaspis. 



As to the Silurine forms , Huxley compared Coccosteus with 

 CJarias and concluded that the structural coincidences in the two 

 forms "must lead us to assign a place near, if not among, the Silu- 

 roidei to Coccosteus''\ 



This view has not met with general acceptance and Traquair 

 writes "Undoubtedly, the weakest point in Professor Huxley's 'Essay' 

 is the attempt which he made to show by comparison of the exo- 

 skeletal plates of Coccosteus with the bones visible on the exterior of 

 the skeleton of many recent Siluroids, that there was a possibility at 

 least of the enigmatical group of the Placodermata turning out to 

 belong to the great order of Teleostei , or ordinary bony fishes, 

 'hitherto supposed to be entirely absent from formations of palaeozoic 

 age'. Recent discoveries in the palaeozoic rocks of America point, 

 as we shall presently see, to another, and perhaps more probable 

 solution of the question." 



The "perhaps more probable solution" is given by the discovery 

 of Dinichthys. Newberry discovered that Dinichthys has a dentition 

 like that of Protopterus, and therefore concludes that it is allied to 

 the Dipnoi. Dinichthys being also allied to Coccosteus, it follows that 

 Coccosteus is allied to the Dipnoi. 



Nevertheless, too much stress must not be laid on a single feature. 

 Fusion of teeth to form great dental plates has occurred over and 

 over again in the Vertebrates as for example in Plectognathi and in 

 Hatteria. The jaws of Dinichthys have far less resemblance to those 

 of the more archaic Ceraiodus, where the teeth lie on the inside on 



