BUPFALO SOCIETY OF NATURAL SCIENCES 91 



The reverse face of both specimens is covered with 

 matrix which cannot be removed, so that the form of this 

 face is unfortunately not to be seen. In the specimen 

 shown in PL 2 7, fig. 6, one of the lateral margins is some- 

 what excavated, as if facetted for articulating with an 

 adjoining element. This is precisely what one would 

 expect in a Dinomylostoma upper dental plate. 



Measurements : 



E 1859 — Length, 46 mm.; greatest height, 18. 

 E 2398 — Length 42 mm.; height, 17 

 Conodont bed (Genesee); Eighteen Mile Creek, near 

 N. Evans, Erie County, N. Y., collected by W. L. Bryant. 



Aspidichthys notabilis Whiteaves 

 (Pis. 25, 26) 



There are several plates in the collection, from the Conodont bed, 

 that bear an ornamentation of large, low tubercles with faint stella- 

 tions at their bases. These plates apparently belong to a single species. 

 In their ornamentation they resemble most the isolated plates described 

 by Whiteaves in 1892, from the Devonic of Manitoba, and named 

 by him Aspidichthys notabilis P The present specimens may, pro- 

 visionally at least, be referred to the same species. The question, 

 however, arises — Are these plates, and those described by W'hiteaves, 

 properly referable to the genus A spidichthys? Whiteaves placed them 

 in this genus with a question mark. 



At the present time, three American Arthrodires are known that 

 have an ornamentation of large tubercles, namely: Trachosteus, 

 Glyptaspis and Aspidichthys. The specimens in hand must there- 

 fore be compared with these three genera. 



As far as the genus Trachosteus is concerned, we have examined the 

 type, which is preserved in the American Museum. The ornamenta- 

 tion of this genus consists of large tubercles somewhat comparable in 

 size with those of the Conodont plates. But these tubercles are 

 higher and more pointed, being in fact denticles rather than tubercles, 

 and with very many more radiations at their bases and in the spaces 

 between contiguous tubercles. In the Conodont bed specimens the 



'9 Whiteaves, J. F.: The fossils of the Devonian rocks of the islands, shores or immediate 

 vicinity of Lakes Manitoba and Winnipegosis. Conlribs. to Can. Palmon., I, 354, pi. xlvii, 1S92. 



