Mineralogy and Geology. 149 



upper part; termination rougli and irregular. Central cavity large, run- 

 ning through nearly the entire length of the spine. Microscopic structure 

 that of very dense ivory -like bone; external surface covered M'ith a thin 

 coating of enamel. 



These spines are, I think, the fin-rays of placoid fishes, but exhibit a 

 character not shown in any other known living or fossil genus, that is, 

 their w^ant of symmetry. They are in pairs, or, at least, are rights and 

 kfts. Spines of this character were collected many years since by Joseph 

 Sullivant, Esq., of Columbus, Ohio, in his quarries in the upper part of 

 the Cliff limestone near that city. A specimen from that locality was 

 exhibted by Mr. Sullivant at the Cleveland meeting of the American 

 Association. Since then, beautiful specimens of one species have been 

 obtained from the same geological horizon in New York, by Prof. Hopkins, 

 figured in the Proceedings of the eightli meeting of the American Asso- 

 ciation, 



Prof, H. is disposed to regard this as the spine of a crustacean ; but its 

 form as well as microscopic structure seem to me to prove it decidedly 



ichthyic. 



If it were any portion of the exoskeleton of a crustacean, it should be 

 tubular throughout, or have an articulation at its proximal extremity, 

 neither of which is true. 



It has every appearance of having been planted in the integiimenta 



without articulation, precisely as are all the dorsal spines of placoid fishes. 



I We miglit suppose these fossils to be the first rays of pectoral fins, but 



'^ in all fishes with which I am acquainted, the pectoral spines are articu- 



lated to the thoracic arch. 



My convictions are that they were worn side by side upon the superior 

 median line, either placed far back, as in Trygon, or farther forward, as 

 in Cktmaera^ Spinax^ Cestracion^ &c. In none of these are there double 

 spines, but in Trygon the spines of the tail arc closely approximated, and 

 it is very probable that such w^as the arrangement of our fossils." 



4. Report on the Economical Geology of the route of the Ashtabula 

 and New Lisbon Railroad ; by J. S. Nkwberry, M.D. Made Nov. 1856. 

 Cleveland, Ohio: 1857. — This Report, which is mainly economical in its 

 L aim, contains important geological information on the coal region, and a 



1^ map and section of the country between Erie and Iludson, south of Lake 



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Erie. 



6. Descriptions of New Fossil Species of MoUusca, 

 F. V. Hayden, in Nebraska Territory : together with a c< 



collected by Dr. 

 complete catalogue 

 of all the remains of Invertebrata hitherto described and identified from 

 the Cretaceous and Tertiary Formations of that region ; by F. B. Meek 

 and F. V. Hayden, M.D. pp- 24. — This is the third paper of these two 

 gentlemen, who have shown themselves so intelligent and successful in 

 the investigation of the Nebraska fossil mollusca. All the papers have 

 been published by the Academy of Natural Sciences at Philadelphia, and 

 have thrown much light on the cretaceous and tertiary formations of that 

 great territory. The last paper possesses even higher interest than the 

 two preceding. Comparing the fossils collected in various sections with 

 those of Nebraska, they show the parallelism of the Cretaceous foima- 

 tions of New Jersey, Alabama, &c. with that of Nebraska, the following 



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