1897.] NEW YORK ACADEMY OF SCIENCES. 301 



hardly be possible to ofive the full and accurate generic defini- 

 tions which are desirable to avoid adding to the great mass of 

 S3'non3'my in Paleontology. 



Formation and locality, Kinderhook group, Le Grand, Iowa. 

 Type in the cabinet of Mr. William F. E. Gurley. 



PsEPHODUS (Helodus) politus, n. sp. 

 PI. XXIV., figs. 13-23. 



Teeth of various forms and sizes, generally oblong with 

 rounded ends, more or less arched in both directions ; root low, 

 parallel with the crown, smooth and often polished below, one 

 side sloping to the edge of the crown, on the other higher, verti- 

 cal, strongly striated ; crown highly polished, uniformly punc- 

 tate, sometimes low and broadly arched in both directions, in 

 other and narrower teeth strongly arched and rising into a 

 rounded boss ; one lateral margin of the crown projecting be- 

 yond the root and terminating in an obtuse edge, on the other 

 side coarsely crenulated. 



The smaller, narrower and more highly arched of these teeth 

 would be accepted as typical specimens of Helodus which are 

 undoubtedly the anterior teeth of various Cochliodont fishes, a 

 good example being Helodus nobilis, the central teeth of Goch- 

 tiodus nobilis, N. & W. described in Vol. II., of the Geological 

 Survey of Illinois, p. 88, PI. VI., both forms occurring in juxta- 

 position. 



With these smaller teeth occur others larger, less strongly 

 arched and in form approaching nearer to those of Psephodus 

 and evidently to be classed generically with Helodus placenta, 

 X. & W., from the Kinderhook group a form which Mr. St. 

 John makes the type of his Psephodus placenta. But the 

 teeth which are now figured and which are alike in the peculiar 

 character of their highly polished and punctate enamel include 

 none that have much affinity with the teeth of Psephodus magnus, 

 Ag. or those of its generic associate Psephodus crenulatus, X. 

 & W., from the Chester limestone of Illinois. I am, there- 

 fore, very doubtful whether they should be included in the same 

 genus, and 3'et more material will be necessary before this ques- 

 tion can be definitely settled. 



Formation and locality, Burlington limestone, Burlington, 111. 

 Type in the cabinet of Mr. William F. E. Gurley. 



Helodus Coxanus, n. sp. 

 PI. XXIV., fig. 24. 

 Median teeth, five or more in a linear series, increasing in size 



