FOSSIL FISHES. 33 



anterior half of tlie upper surface is mostly smooth. The posterioi- half and 

 margins of the antei-ior 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 Coccosteus 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 Placoderm, 

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

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

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

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

 with that of the dorsal plate of Coccosteus cuspidatus, Agass., on the same 

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

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

 plate of tlie ventral 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 that it held a central position in the ventral shield of 

 some Placoderm allied to Pterichthys and Coccosteus. 



For comparison with this, representations of the external and internal 

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

 4 « of Plate LIY. 



The discovery of the remains of C6>c'C067'ews in the Devonian rocks of 

 America is a fact of interest as adding another 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 Red 

 Sandstone of Scotland, and has been met with in Russia 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 this absencG, however, in the Palaeontology of our first volume, by 

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

 land were taken from a different meniber 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 Red Sandstone is of later date, and is a 

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

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

 costeus, Pterichthys, and the scaled Ganoids, Osteolejns, Diptertis, etc., as 

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

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



