122 PISCES. 



Sub- Order 14. Plectognathi. 



Both the Gymnodonts and Scleroderms seem to have been 

 already differentiated in early Eocene times, and they have 

 subsequently exhibited very little change. Jaws indistinguish- 

 able from those of Orthagoriscus have been found in the Upper 

 Eocene (Oligocene) of Belgium. Fishes closely resembling 

 Diodon, Ostracion, and Batistes occur in the Upper Eocene of 

 Monte Bolca. 



