CLASSIFICATION OF DEVONIAN FISHES. 



35 



of each side being closely united, or even amalgamated together, 

 while the opposite pairs are joined, in the middle line, by a strongly 

 serrated suture. 



Fig. 21. 



Hyoidean and Pectoral Plates of 

 Clarias. Coccosteus. Loricaria. 



When the pect oral fin is provided with an anterior spine, this is 

 articulated by a curiously complicated joint with the so-called 

 coracoid. The cornua of the hyoid are large stout bones, and the 

 urohyal,also a large and strong bone, which is particularly broad in 

 Loricaria, connects the hyoidean with the pectoral apparatus. 



On comparing this apparatus with the sternal shield of Coccosteus, 

 one is tempted to compare the antero-median piece of the latter 

 with the urohyal of the Siluroid, the ant ero -lateral piece with the 

 " coracoid," and the postero-lateral piece with the so-called " radius,'' 

 the more especially as the antero-lateral piece corresponds with that 

 part of the thoracic shield of Pterichthys which supports the plated, 

 appendage representing the pectoral fin, in that genus. 



On the other hand, it must be confessed that the closer connexion 

 of the antero-median piece with the thoracic plates than with the 

 hyoidean cornua, and the very backward position of the postero- 

 lateral pifites, apparently out of reach of any connexion with the 

 fins, militate against this view ; which, in addition, leaves the 

 median rliomboidal plate unaccounted for. 



The bones Mn. are, of course, as has long been determined, the 

 rami of the mandibles of Coccosteus. Their singular figure is not 

 unlike that of the corresponding bones in Loricaria. Finally, 

 the long flat bones a (fig. 21), I have no doubt, are the chief 

 parts of the hyoidean arch, which are also proportionately large in 

 many Siluroids. 



No one, I think, will deny that the structural coincidences here 



