226 PALEOZOIC FISHES OF NORTH AMERICA. 
Formation and locality: Coal Measures, Decatur, Macon County, Il. 
Collected by Mr H. A. Wheeler, of Washington University, Saint Louis, to 
whom I owe the opportunity of examining and describing it. 
CTENODUS SERRATUS, Newb. 
Plate XXVII, Fig. 31. 
Ctenodus serratus, N.; Paleontology of Ohio, vol. 2, p. 59, pl. 58, figs. 15, 16. 
Teeth of lower jaw of medium size, sixteen lines long by nine lines 
wide, somewhat triangular in outline; crown marked with eight prominent 
and sharp radiating ridges, which terminate above in numerous compressed, 
acute denticles, the furrows between the ridges being pitted to receive cor- 
responding denticles of the opposite teeth. These ridges and furrows vary 
much in length, so that the end of the tooth forms a long-pointed triangle, 
and at the opposite extremity the crown is rounded and the base projects in 
a depressed and flattened point. 
In general form and marking this tooth bears considerable resemblance 
to that of Ct. obliquus of the Northumberland coal-fields, England, but the 
ridges are more numerous and much narrower. From the larger species of 
Ctenodus found in England, Ct. tuberculatus, ete., it will at once be distin- 
guished by the fan-like radiation of its ridges, which all center at the most 
prominent point of the crown. When in its perfect condition this is the 
most elegant species of the genus yet discovered. It is characterized by a 
remarkable exactness of form and sculpture. The internal margin forms a 
graceful arch, from which the prominent point of the base projects at the 
end of the tooth where the ridges are shortest. The denticles which crown 
the ridges are much compressed, very sharp, and somewhat curved outward. 
Formation and locality: Coal Measures; Linton, Ohio. 
Crenopus OHIOENSIS, Cope. 
Prof. Edward Cope, in 1874, briefly described in the Proceedings of the 
Academy of Natural Sciences, Philadelphia, a portion of the cranial bones 
of a species of Ctenodus from the Coal Measures of Linton, Ohio. He called 
the species Ct. Ohioensis, and illustrated it further in the Paleontology of 
