212 IOWA GEOLOGICAL SURVEY 



ing them in a rough way from those of the Carboniferous age. 

 Still, the type which is predominant in the Carboniferous occurs 

 in the Devonian, where may be also found as exceptions the 

 smooth-ridged species of the Mesozoic. ' ' He accordingly adopts 

 the arbitrary method of classifying "all the older Dipterines as 

 belonging to the genus Dipterus, the Middle and Upper Car- 

 boniferous species as Ctenodus, the Triassic as Ceratodus; but 

 it would be quite impossible to give any satisfactory generic 

 definitions to these different groups."* 



In all, six species of Ctenodipterines were established by New- 

 berry upon the evidence of detached teeth occurring in the 

 Chemung of Warren, Pennsylvania, and four upon similar re- 

 mains from the Catskill of Tioga and Bradford counties, in the 

 same State. Still earlier than any of these, the undefined name 

 of Dipterus ithacensis had been proposed by H. S. Williamsf 

 for certain doubtful remains discovered by him in the New York 

 Portage, making a total of eleven species that have been recog- 

 nized in the Appalachian Upper Devonian. Besides these, a 

 solitary species (Ctenodus wagneri Newb.) has been described 

 from the Cleveland Shale of Ohio, and four from the Iowa De- 

 vonian, two from the middle, and two from the upper members 

 of the series. The names of the various Ctenodipterine species 

 that have been proposed or described from the Devonian rocks of 

 this continent up to the present time may be tabulated in order 

 of stratigraphic succession as follows: 



NORTH AMERICAN SPECIES OF DEVONIAN CTENODIPTERINES 



Catskill G-kotjp. 



Dipterus contraversus Hay (=D. radiatus Newb.). Tioga 

 county, Pennsylvania. 



Dipterus fleischeri Newb. Bradford county, Pennsylvania, 

 and Delaware county, New York. 



Dipterus sherwoodi Newb. Tioga county, Pennsylvania. 



Sagenodus angustus (Newb.). Near Leroy, Bradford county, 

 Pennsylvania. 



*Monogr. U. S. Geol. Surv. 1889, 16. p. 88. 



tProc. Amer. Assoc. Adv. Sci., 30th meeting, 1882, p. 192. 



