The Chondrostei and Holostei 



335 



odus, Coccodus, Palaeobalistum^ and Pycnodus are met with 

 in marine strata, from the Greensand and Cenomanian up 

 to beds of the Miocene, when the last named and lingering 

 genus disappears. Thus in the marine beds of Mt. Lebanon 

 in Syria, in the Senonian of England, France and Bohemia, 

 in the Monte Bolca beds of Upper Eocene age in Italy, as 

 well as elsewhere, more or less perfect remains of species 

 belonging to some of the above genera, have been secured. 

 On the accompanying chart the above striking strati- 

 graphic and evolutionary procession of the Pycnodonts is 

 set forth as perfectly as our present very fragmentary 

 knowledge of the number of species hitherto recorded per- 

 mits. But future vigorous investigation of each strati- 

 graphic zone, in connection with the organic remains of it, 

 may somewhat alter — though we believe not fundamentally 

 — our present conceptions. 



The Pachycormidae as a group seems to possess a 

 special evolutionary significance that is as suggestive as is 

 its range in time and space. For from genera like Eugna- 

 thus and Caturus of the family Eugnathidae, that range 

 from Lower Liassic up to Purbeckian times, derivative 

 forms branched off that took on more and more the struc- 



