FOSSIL FISHES. 59 



found in rocks older than the Jurassic. I am happy to be al . to say, 

 however, that the views there expressed in regard to the zoological rela- 

 tions of this genus are fully confirmed by Sir Philip Egerton, who has 

 made a special study of the Chimseroids, living and fossil, and is con- 

 fessedly the highest living authority in all that relates to their structure 

 and classification. He writes me that the teeth described in Vol. I., Part 

 II., pp. 307-313, under the name of Bhyndhodus, are unquestionably those 

 of ChiniEeroid fishes. 



PrSCTODXJS CALCEOLUS, N. AND W. 

 Plate LIX., Pigs. 13, 13 a. 



A tooth which probably belongs to the same species with that now fig- 

 ured, was described in the Illinois Greological Report, "Vol. IL, p. 106, 

 Plate X., Fig. 10, under the name of liinodvs caloeolus. This name was 

 subsequently (Vol. IV., p. 374) changed to that given above, as it was dis- 

 covered that the tooth designated by it came within Pander's genus 

 Ptyctodus. 



During the past year I have received from. Mr. A. S. Tiffany, of Da- 

 venport, Iowa, the specimen of which a figure is now given. This is 

 longer and narrower than that described in the Illinois Report, and the 

 triturating surface instead of being depressed or sunken into the crown 

 of the tooth, as in the Illinois specimen, is distinctly raised above the 

 general surface. This difference is, I suspect, due to the fact that one is 

 an upper and the other an under tooth ; the elevated portions of one fit- 

 ting into the depressions of the other. 



As stated in the description contained in the Illinois Report, I suppose 

 these to be the teeth of Chimseroid fishes. 



Formation and Locality : Hamilton Group, Davenport, Iowa. 



GANOIDEI. 



DIPTEBINL 



Genus CTENODUS, Agass. 



Ctenodxjs SEERATTrs (n. sp.). 



Teeth of lower (?) jaw of medium size, 16 lines long by 9 li: is wide, 

 somewhat triangular in outline ; crown marked with eight prominent and 



