BUPFALO SOCIETY OF NATURAL SCIENCES 107 



Conodont bed, (Genesee) ; Eighteen Mile Creek, near 

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

 Bryant. 



E 2440 A fragment similar to the preceding, 3.5 cm. in length (fig. 

 37 A), with narrower ridges and the spaces between them 

 somewhat wider than in the preceding (one-third to one- 

 half the width of the ridges). 



Formation and locality same as preceding. 



CYCLIC 



Palseospondylus gunni Traquair 



E 2441 A specimen showing the head and vertebral column in great 



perfection, but lacking detail in caudal fin. On the same 



slab is a poor specimen of Mesacanthus peachi (Egerton). 



Middle Old Red Sandstone; Achanarras, Caithness, 



Scotland. 



PTYCTODONTID.ffi 



The family Ptyctodontidae is known only by dental plates and 

 isolated tritors. Associated with them are plates of various genera — 

 e. g., Acanthaspis, Eczematolepis^a.nd the suggestion has been made 

 that these are the body-plates of the fishes to which these dental 

 plates belonged. However, conclusive proof of this is not yet at 

 hand, and for the time being we must continue to refer to the body- 

 plates and the dental elements under separate names. 



There are three genera of the Ptyctodontidse: (i) Ptyctodus, with 

 the elitire, or almost entire, oral margin formed into a grinding tritor; 

 (2) Rhynchodus, with oral margin a cutting blade; (3) Palceomylus, 

 with a grinding tritor, but the element is much larger and differently 

 formed from that of Ptyctodus. Of these genera, the first and third 

 are confined to the Devonic, while the second ranges into the Car- 

 bonic. 



The genus Rhamphodus, described by Jaekel from the Eifel Devonic 

 is apparently identical with Rhynchodus, as was pointed out by 

 Eastman.^^ 



In addition to these there is a new form described as a new genus on 

 a subsequent page of this catalog. 



<* ' 'Devonian fishes of Iowa." Ann. Kept. Iowa Geol. Survey, xviii, 127-129, 1908. 



