GEOLOGY. 321 



lands as different. Yet the identity of date of the two drift formations should 

 not be dogmatically pronounced upon in the present incomplete condition of 

 comparative geology. 



INTERESTING FOSSILS. 



At the last meeting of the American Association. President Hitchcock, ex- 

 hibited the jaw of a fossil fish which he had received from the coal-fields of 

 Illinois. The specimen was about a foot long, curved like a saber, and on 

 its edge were set, in sockets, seven teeth with serrated edges. It was found 

 about three inches above a bed of coal three or four feet in thickness, making- 

 it certain that it was in the coal measures. Professor Agassiz said that this 

 was one of the most interesting specimens he had ever seen. The idea of a 

 shark was at once suggested, and yet it could not be a shark for this reason, 

 that although the shark had teeth in seven rows yet they were not set in a 

 socket, and they were behind each other, not by their edges but by their flat 

 surfaces. Moreover, no shark had teeth in his upper jaw, if we understood 

 by that term what was understood in higher animals. The bones of the 

 upper jaw were in charts reduced to cartilages at the sides of the mouth, and 

 the palatine bones which in higher animals formed the roof of the mouth were 

 in sharks set with teeth. Sharks' upper teeth were, therefore, palatine teeth 

 and not jaw teeth. But in some sharks, as in skates, we had the beaks uni- 

 formly pointed. In the saw-fish the beak projected with a double row of 

 teeth at the sides in sockets, and this was the only type in which any thing 

 similar to the fossil could be observed. Furthermore this bone when sub- 

 jected to the microscope was found to be made up of the same hexagonal 

 tissue, to have the same tesselated structure as the cartilage of sharks and 

 skates and the saw of the saw-fish. He concluded, therefore, that this was a 

 projection from one side of the shark's head, and its point met a correspond- 

 ing projection from the other side, both forming a semicircle in front of his head. 



Professor Agassiz also stated that the general result of his comparison of 

 the fossil fishes of the American coal measures was, that there were two very 

 different kinds of fishes, one represented by the very metamorphic fragments 

 now on the table, and identical in its character with that which Dr. Newberry 

 had found in Ohio, the other in southern Illinois, whence Dr. Cassidy had sent 

 him a number of fossils, among which were ten or twelve species of fish, as 

 many as were generally found in a water basin after fishing for one season. 

 The fish found here were identical in their character with those of Bristol in 

 England. The two were as different as the fish fauna of the Baltic and 

 Mediterranean, or the Mediterranean and the Red Sea. 



President Hitchcock also exhibited a series of footmarks of an animal which, 

 from analogy, he had called a Batrachian. It was web-footed, and the web 

 extended beyond the toe. It was a two-legged frog, with feet twice as large 

 as an elephant's. They had in Europe the Labyrinthodon, which was as large 

 as an ox, but he was a mere pigmy compared with this. What he had 

 formerly considered a nail he was now convinced was but a protuberance. 



Professor Hall remarked in this connection that he was convinced that 



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