OKAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 43 



cinidae, and Cyprinidae, must be founded under the term Ostari- 

 ophyseae, since they possess iu common the remarkable " Weber's 

 apparatus." No weight can then be assigned to characters of the 

 dermal armature or fins. Bridge and Haddon, also working on 

 Weber's apparatus, seem also to accept the modern origin of Siluroids. 



Thus, according to Sagemehl, the Siluroids are to be derived from 

 Amia. Such a view seems to me inconsistent with all known principles 

 of comparative anatomy and geographical distribution. 



Any discussion on the affinities of the Siluroids would be incomplete 

 without reference to the paleontological evidence. 



Agassiz classed the Siluroids, on account of their dermal armature, 

 with the Ganoids, from which they were removed by Johannes Miiller. 

 Subsequently (1858-61) Huxley following up the investigations of 

 Pander, compared certain of the Siluroids with Gephalaspidae. " No 

 one can overlook the curious points of resemblance between the 

 Siluroids, Caliichthys and Loricaria, on the one hand, and Cephalaspis 

 on the other, while in other respects, they may be still better under- 

 stood by the help of the Chondrostean Ganoids." " I am inclined to 

 place the Cephalaspids provisionally among the Chondrostei, where 

 they will form a very distinct family." Ray Lankester at the con- 

 clusion of his monograph on the C ephalaspidae remarks : " It cannot 

 be too strongly asserted that these fishes are, 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 Amphirhine fishes." "The series of scales or bones along the body 

 of Cephalaspis — so strongly recalling the cinctures of Caliichthys 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 

 C ephalaspidae stand alone." 



Pander, Huxley, and Ray Lankester are therefore agreed that the 

 dermal armature of Loricarina is like that of the oldest known 

 vertebrate fossils. 



Claypole (1892) has discovered Crossopterygian fins along with 

 a Pteraspidian, Palaeaspis. 



As to the Silurine forms, Huxley compared Coccosteus with Clarias 



