From Eocene to Recent Time 239 



goes, In their ancient genera but only in evolved and de- 

 rivative genera from these that managed to persist. Thus 

 the Scopelidae are known to us by eight genera in the 

 Cretaceous, and they seem thereafter to have become large- 

 ly decimated or modified, to reappear only in the Oligocene 

 and Miocene strata of Switzerland and Northern Italy 

 as the genera Scopeloides^ Parascopelus and Anapterus. 

 The Berycidae show six Cretaceous genera — for Beryx 

 seems to be wrongly credited to the Cretaceous — which then 

 become largely blotted out, to reappear as MyripHstis and 

 Holocent7-iim of the Upper Eocene. 



In contrast to the above, the elasmobranch fishes that 

 passed from freshwaters into the sea during Jurassic and 

 Cretaceous times, are represented by fifteen genera, which 

 have persisted at least from the latter period on through 

 the Eocene to the present day. These are Acanthias, Cen- 

 trophonis, Squatina, Rhinobatus,, Raja, Cyclohatis, Noti- 

 damis, Cestracion, ScyUiiim, Pristiurus, Scapanorliynchus, 

 Odontaspis^ Oxyrhina, Ginglymostoma, and Larnna. Vari- 

 ous reasons might be given for such differences in relative 

 persistence. 



In addition to marked deformations by volcanic agency 

 at the beginning of the Eocene period, ample proof exists 

 of continued volcanic action during deposition of these 

 beds In many countries. 



But toward the close of the Eocene and in early Oligo- 

 cene time, some phenomenal displays of earth-movement 

 and volcanic activity took place, which would largely ex- 

 plain the profound changes witnessed in the animal life, 

 and not least in the fish life of those days, as compared with 

 the late Oligocene and Miocene periods. Thus a large 

 part of South Europe, North Africa, South Central Asia 

 on to Japan, the Philippines and Sumatra at least, formed 

 a great and continuous sea during Eocene time, and which 

 is approximately outlined in the chart (Fig. 35). 



In this sea the huge foraminifer Niimmulites became 

 the prevailing marine organism, while in part by accumula- 

 tion of calcareous nummulitic tests, In part by activity of 

 calcareous bacteria, deposits were formed that range from 

 100 to 3,000 feet in thickness. At this time the Pyrenees, 



