80 Dynamic Theory. 



CHAPTER X. 



DEVONIAN AGE OF FISHES. 



In this age we come to new general forms of life. The lower Period 

 is called the Oriskany. The strata are sandstone, in some places several 

 hundred feet thick. Their organic remains are in great profusion, but 

 all are of the families represented back in the Silurian, Brachiopods, 

 G-asteropods, Trilobites, Orthocerata, Crinoids and Cystids, &c. Old 

 forms but new genera and species. The next Epoch is the Cauda Galli. 

 This is so called from the abundant remains of a peculiar sea-weed of 

 the Fucoid Algae family, shaped like the tail of a rooster. 



There are also beds composed of Protophite Algae Desmids and Dia- 

 toms. They are very abundant, but very minute, running from one- 

 five-hundredth down to one-five-thousandth of an inch in diameter. 



In the Upper Helderberg period, we find a new Brachiopod family, the 

 Productus, which expires in the Permian period. There are also new 

 species of Trilobites and Mollusks. But the most interesting are the 

 Vertebrate remains. 



These consist of the remains of fishes belonging to two of the three 

 general orders of fishes, viz. , the G-anoids and the Selachii or Placoids. 

 They are found in the Schoharie grit about the middle of the Cornif erous 

 period of New York, and the corresponding strata in Ohio, Indiana and 

 elsewhere. The remains are very abundant and some of the specimens 

 are very large as much as fifteen to twenty feet in length. 



On top of the Corniferous strata come the Hamilton, 1,200 feet thick, 

 and the Chemung, 1,400 feet thick. The first insects yet found are in 

 New Brunswick, in strata corresponding to Hamilton or Chemung of 

 New York. They are Neuropters insects < ' having four similar mem- 

 branous reticulated wings, as the species of Dragon-fly or Libellula, 

 Termes, Phryganea, Ephemera." Those of the Devonian seem to be 

 Ephemera. Their presence is evidence of the existence of dry land and 

 land vegetation. 



In the Hamilton beds are the first undoubted specimens of land plants 

 in America. They consisted of Sigillaria and Lepidodendron, both sup- 

 posed to be related to the Ground Pine family. This period also pro- 

 duced a large new Cephalopod the Groniatites; an advance genus of the 

 Ammonites, a family that had a very large representation in Mesozoic 

 times. But there were no vertebrates in the Hamilton, nor were there 

 any in the Chemung period, although marine life was there as well rep 

 resented as anywhere below. There was a great difference in the 



