238 WALKS AND TALKS. 



Limestone. The body of the fish was covered with rounded, 

 overlapping, bony scales nearly circular in outline, and about 

 an inch in diameter. 



Please notice that these oldest American fishes, dating 

 from the Corniferous Period, are Elasmobranchs and Ganoids. 

 Of the former, there were two types, Cestracionts and Chi- 

 mseroids. Of the latter, also two types related to sturgeons 

 and gar-pikes. 



I must now inform you that fish-like creatures began exist- 

 ence earlier in the Old World than in the New at least, 

 that is the opinion long entertained, though we shall probably 

 have to abandon it when our information is more complete. 

 In the Upper Ludlovv rocks of England, which form the 

 upper part of the Silurian, is a "bone-bed" composed almost 

 entirely of the remains of fishes, much triturated and matted 

 together. From this bed spines of On'-chus have been 

 obtained a fish apparently belonging to the Cestraciont type 

 of sharks. In the Upper Ludlow have been found, also, por- 

 tions of Ceph-al-as'-pis, or "Shield-head," having the head 

 covered by a broad plate. This fish was intermediate between 

 Placoderms and Ganoids. Still lower down in the "Lower 

 Ludlow," relics of a similar fish called Pter-as'-pis or "Wing- 

 shield" have been found. So we say the oldest fishes of 

 Great Britain lived in the Silurian Age. We know also, that 

 very similar fishes dwelt contemporaneously in the waters 

 which covered Russia and Bohemia. 



I have next to inform you that this record is beaten by 

 America. It has very recently been announced by Professor 

 Claypole that the Corniferous Period was rwt the earliest date 

 of American fishes. He finds remains of fishes in the lower 

 and upper portions of the Salina Group of Pennsylvania. 

 They appear to be related to Placoderms and Ganoids, and he 

 has bestowed on them the name Pal-ce-as'-pis or "Ancient 

 Shield." Still lower than this he reports some fish remains 

 which he thinks may be referred to the genus On-chus. These 

 are at the bottom of the Clinton Group, which in Pennsyl- 

 vania is fifteen hundred feet below the Corniferous Limestone, 



