44 PALEONTOLOGY OF OHIO. 



the Myfnoidp, they wonld certainly be preserved. Possibly some other 

 relics of Cyclostonious fishes will yet be found, but with the facts now 

 before ns we seem justified in concluding that if the Conodonts are not 

 the remains of Marsipobranchs, these vei'tebrate animals, though verv 

 low iu the scale of beings, are, like Fungi, Lichens and Mosses among 

 •plants, of modern date. If, however, the view now proposed be proven 

 true, in the Conodonts of the St. Petersburg Silurian marls, described 

 by Pander, those of the Mountain limestone of England, collected in 

 such numbers by Moore, and in those of the Waverly of Ohio, we have 

 a very respectable representation of this group of fishes in the Palaeo- 

 zoic faunas ;/ for they exhibit so great a variety of form that if thej' are 

 the teeth of fishes they are the relics of many genera and species. This 

 hypothesis encounters a difficulty in the fact that while the Conodonts 

 are calcareous, the teeth of the living Cyclostomous fishes are horny or 

 chitonous. It is quite possible, however, that the ancient species had cal- 

 careous teeth, and in that respect differed from the modern ones ; just as 

 the calcareous sponges, so common in the Palaeozoic seas, have, for the 

 most part, been superseded by those having horny tissues containing silic- 

 eous spicules. 



A similar objection may be urged against the theory that the Conodonts 

 are the teeth of Mollnsks, as the modern MoUusca have siliceous teeth. 



More proof must be gathered before it can be positively asserted that 

 the Conodonts are teeth of Marsipobranchs, but they resemble them so 

 closely that it seems at least possible that we have in these delicate organs 

 the teeth of small Lampreys, or Hags, which inhabited the Palaeozoic 

 seas in large numbers. If this is their true nature, they represent the 

 first fishes that existed on the globe ; unless, indeed, they were preceded 

 by the progenitors of Am.phioxus, and they, like the living Lancelot, 

 were without hard parts, and could leave no trace of their existence. - 



ELASMOBRAJfCHII. 



Genus DIPLODUS, Agass. 



In the notes on Biplodus published in the first volume of this Eeport 

 (Part L, p. 334), three species found in Ohio ai-e described, but no fig- 

 ures of them' are given. These are all now figured on Plate LVIII. Figs. 

 1, 1 a, 1 i, represent Diplodiis latus ; fine specimens of which have been 

 obtained from Linton during the past year. As will be seen from the 

 figures, this species may be readily recognized by its large size, its broad. 



