118 CATALOG OF FOSSIL FISHES IN THE MUSEUM 



Formation and Locality. — Conodont bed (Genesee) ; Eighteen Mile 

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

 Bryant. 



Dental plate subquadrangular, the upper margin more or less 

 parallel to the lower; symphyseal margin making an angle of about 

 135° with the inferior margin. Oral margin a cutting blade bevelled 

 by wear on outer face, with a small beak-like projection at its anterior 

 extremity. Symphyseal face bent inward at right angles to the outer 

 face and forming a smooth symphyseal facet about 3 mm. in width, 

 extending downward for about two-thirds the height of the plate, 

 and terminating on its innermost margin in two protuberances, of 

 which the lower one is the larger. Cross-section of dental plate 

 thickest at about one-third its height from the bottom, where it 

 measures 5 mm., and gradually thinning out towards the cutting 

 edge; inner face strengthened by very faint ridges. Outer as well as 

 inner faces of plate ornamented with fine lines running parallel to the 

 long axis; these lines connected with one another at frequent intervals 

 and appearing under the glass as a fine reticulated network; this 

 ornamentation extends almost to the cutting edge of the plate where, 

 however, it is mostly obliterated through wear. In one of the two 

 cotypes, the ornamentation can be clearly seen curving around the 

 front margin of the plate below the symphyseal area. 



Remarks. — These two dental plates indicate a highly differentiated 

 species of Rhynchodus. This is easily distinguished from all other 

 species by the remarkable ornamentation and the peculiar form. 

 In neither specimen is there any indication of a spiniferous process 

 below the front of the plate. 



The symphyseal facet is unusual and worthy of comment. It is 

 bent in at right angles to the outer face of the plate and formed as in 

 Coccosteus, except that the five or six symphyseal denticles of the 

 latter, are represented by only two low denticle-like protuberances. 

 It cannot be made out whether the symphyseal edges wer eunited, or 

 were free and more or less functional. They do not show any lines 

 of wear. 



E 1947 Two dental plates apparently referable to Rhynchodus or- 

 nattis, remarkable for the ornamental tubercles on the 

 outer face (PI. 39, figs. 3, 3a, 4, 4a). 



E 1947a Conodont Bed (Lower Genesee) ; Eighteen Mile Creek, Erie 

 County, N. Y. Collected by W. L. Bryant. 



