FOSSIL FISHES. 33 



anterior half of the upper surface is mostly smooth. The posterior half and 

 margins of the anterior portion are set with relatively fine crowded tubercles. 



The specimen now described gives us the first intimation of the exist- 

 ence of the remains of OocGOsteus on the North American continent. 

 This was obtained by Mr. J. H. Klippart from the Corniferous limestone 

 at Delaware, Ohio. It is plainly the post-dorsal shield of a Flacoderm, 

 and corresponds so closely in size, form, and markings with the terininal 

 shield of the carapace worn by some species of CocGosteus that I have 

 little hesitation in referring it to that genus. The resemblance to which I 

 refer will be seen by comparing the figure of the fossil now described 

 \\ith that of the dorsal plate of Coocosteus cuspidatus, Agass., on the same 

 plate and drawn from a specimen recently received from Scotland. A 

 single rliomboidal plate shown on Plate LIY., Fig. 2a, may be the central 

 plate of the venti-al shield, but unfortunately only its inner surface is 

 shown, and from this we should be unwarranted in pronouncing it a plate 

 of Coccosteus. There is good reason, however, for believing this to be 

 the case. It certainly does not belong to the bony structure of any of 

 the more common fishes of the Corniferous limestone, and its symmetri- 

 cal form indicates tliat it held a central position in .the ventral shield of 

 some Placoderm allied to PtericMhys and Coccosteus. 



For comparison with this, representations of the external and internal 

 surfaces of the ventro-median plate of Coocosteus are given in Figs. 4, 

 4 a of Plate LIY. 



The discovery of the remains of Coccosteus in the Devonian rocks of 

 America is a fact of interest as adding anotlier to the forms of ancient life 

 common to the old and new worlds ; but it has been long expected, and, 

 since this is one of the most characteristic fossil fishes of the Old Eed 

 Sandstone of Scotland, and has been met with in Kussia and Bohemia, 

 its absence from all collections of fish remains heretofore made in this 

 country has been a matter of some surprise. I have offered an explana- 

 tion of tliis absence, however, in the Palaeontology of our first volume, by 

 suggesting that the fish remains found in the Old Eed Sandstone of Scot- 

 land were taken from a different member of the Devonian system, and 

 from deposits of a different character from that— the Corniferous lime- 

 stone—which has furnished most of our Devonian fishes. The Cornifer- 

 ous limestone is the central member of the system, and is an open sea 

 deposit, while much of the Old Eed Sandstone is of later date, and is a 

 shore deposit, formed either in fresh water, as supposed by Prof. Eamsay, 

 or in bays or gulfs. I have suggested, therefore, that the remains of Coo- 

 costeus,' PtericMhys, and the scaled Ganoids, Osteolepis, Dipterus, etc., as 

 well as tlie Acanthodeans, so common in Europe, and heretofore not 

 found in this country, would probably be discovered in the Oatskill and 



