BUFFALO SOCIETY OF NATURAL SCIENCES 151 



them as would be expected if they were comparable with the usual 

 palatine and splenial dental plates of dipnoans. On the other hand, 

 they are not of the form to compare with dipnoan plates like PaloB- 

 daphus, in which the upper and the lower dental elements are united 

 into single symmetrical plates. The S}mthetodont elements rather 

 give the impression of belonging to some sort of dental pavement such 

 as is found in certain Paleozoic sharks. 



We may mention here that it seems to us also, that the dental 

 plates from the Upper Devonic of Iowa, referred by Eastman^^ to 

 McCoy's genus Conchodus, are also not dipnoan, for they show neither 

 rows of tubercles nor ridges. And their small, postero-lateral pro- 

 longation regarded by Eastman as the vestige of a dipnoan denticled 

 ridge, is nothing more than the postero-lateral termination found 

 in many forms of grinding shark teeth, for instance, in Deltodus. 

 The Conchodus elements may belong to the same pavement as the 

 synthetodont plates. 



To conclude, from the evidence at hand the dental plates named 

 Synthetodus do not show the characteristic structure of dipnoan dental 

 plates. They lack the dipnoan radiating ridges or rows of tubercles. 

 Their bilaterally symmetrical form, large central boss (or its equiva- 

 lent, the tripartite division of the wearing area), are features strongly 

 suggestive of certain shark pavement teeth, e. g., Helodus. And, for 

 the present Synthetodus may, provisionally at least, be placed in the 

 shark family Cochliodontidae. 



E 2017 An imperfect dental plate from the center of which rises a 

 large smooth boss (PI. 55, figs, i, 2). The surface is 

 highly polished and covered with a scattering of small 

 punctae. The under side is roughened with depressions 

 and pustules. 



Conodont bed (Genesee); Eighteen Mile Creek, near 

 North Evans, Erie County, N. Y. Collected by W. L. 

 Bryant. 



Acmoniodus clarkei, n. gen., n. sp. 



(PI. 55, fig. 3; text-fig. 53) 



One of the most peculiar fish remains in the collection is the speci- 

 men from the Conodont bed at Eighteen Mile Creek, represented in 

 Plate 55, figure 3, and in text-figure 53. It is clearly a dental element, 



** Devonian fishes of Iowa, 228-229, 1908. 



