Summary of Conclusions Reached 521 



of these fishes is given from the elaborate "Thiolliere" 

 memorial volume. The holostean group Lepidosteidae 

 probably evolved amid the great Cretaceo-Eocene lakes of 

 N. America, migrated eastward into Central Europe in late 

 Eocene time, died out in the latter area in the late Miocene, 

 but now persists in three or four species that are scattered 

 from the North-Eastern States to Mexico. 



The gano-teleostean genera that form the division 

 Isospondyli are undoubtedly the highest of the series, as 

 they are also the latest to appear. They, along with the 

 already advanced members of the previous division — the 

 Protospondylii — must have stocked abundantly the rivers 

 and lakes of Upper Triassic age in Europe, Asia, Africa, 

 and even Australia. A striking feature however is that 

 the earlier and more primitive Isospondyli are wholly ab- 

 sent from the American continent, so far at least as we at 

 present know, though the individuals of such genera as 

 Pholidoplwrus and specially Leptolepis must have swarmed 

 in countless numbers over inland waters of the above conti- 

 nents. 



Chapter 12. The soft-finned Teleostei in time and space. 



It is postulated that since primitive ganoid ancestors of 

 the Teleostei were, and remained as, inhabitants of fresh- 

 waters, the descendant soft-finned teleosts must have origi- 

 nated amid like environment. The entire history of the 

 group demonstrates this. Further the ancestral gano- 

 teleosteans early split up into two evolving and diverging 

 lines. The older of these that wholly or largely retained 

 soft fin-rays have had the convenient term retained of 

 Malacopterygii, the newer and more evolved is called the 

 Acanthopterygii. The former includes the largest number 

 of existing freshwater teleosts. These all retain the soft 

 fin-rays, the positions of pectoral and pelvic fins, the fre- 

 quent cycloid scaling, the degree of ossification, and other 

 Inherited ganoid characters. The Acanthopterygii, that 

 have become largely marine, show change and advance on 

 these characters. It Is again emphasized that the South 

 American, and to large extent the North American conti- 



