CORNTFEROUS PERIOD. 



275 



Fig. 458. 



found in Tennessee ; it is a third American genus of the Terehratula family, 

 —Striclclandia and Bensselaeria being the first two. Two small species of Pro- 

 ductus have been collected by Billings in Canada, and one by Jewett in the New 

 York Corniferous. 



(b.) Conchifers. — Fig. 456, Lucina ? proavia, also occurring in Europe ; fig. 457, 

 Conucardium triyonalc of both New York and the West. 



(c.) Pterojjods, Gaatercpods, and Cc- 

 phalopods. — Pteropods are represented 

 by the Tentaculites scalaris. There are 

 also several species of Gasteropods. Fig. 

 458 is the Platyceras dumosum of the Cor- 

 niferous in New York. 



A few Orthocerata occur in the beds. 

 The Cyrtoceras undulatitm, a large shell 

 coiled in a plane, is supposed, as the name 

 implies, to be related to the Cephalopods. 



3. Articulates. — Trilobites are the 

 only Articulates known. The most com- 

 mon species are the Dalmania (Odonto- 

 cepthalns) selenurus, having a two-pointed 

 tail; and the Proeius (Calymene) crassi- 

 marginatus, having the posterior margin of the body (the pygidium) thickened 

 and rounded. 



The Schoharie grit is closely related in its fossils to the limestones above, 

 and contains but few species that are not found in the latter. 



4. Vertebrates — The remains of the earliest of Vertebrates, Fishes, ap- 

 pear first in America, according to present knowledge, in the Schoharie grit ; 

 and many species are known from the later epoch of the Corniferous period, 

 both in New York and the more western States of Ohio, Indiana, etc. Some of 

 these remains are represented in the annexed figures. Fig. 459 is the fin-bone 

 of a large shark ; fig. 460, the head of a fish related closely to the Pterichthys of 



Platyceras dumosum. 



Fie:. 459. 



Fin-spine of a shark (X %)• 



Stromness, drawn by Dr. Newberry from a specimen found at Sandusky, Ohio; 

 and fig. 461, the tooth, natural size, of probably this formidable species. Dr. 

 Newberry estimates its length at six or seven feet. A specimen was earlier 

 found by Dr. Norwood at Madison, Indiana, and named by Owen & Norwood 

 Macropetcdichthys (Am. Jour. Sci. [2] i. 367, 1846). It is near the genus Ho- 

 mostius described by Mr. Asmuss, of Dorpat, in 1833 and 1837. As shown in the 

 figure, the genus differs widely in the sutures of the buckler from Pterichthys 

 (fig. 516). Asterolepi-i of Eichwald has the priority of Pterichthys ; but it was 

 based on a fragment only, and was published without a description. 



