THE PERMIAN FISHES OF NORTH AMERICA 163 



DIPNEUSTI. 



Genus SAGENODUS Owen. 

 Trans. Odontol. Soc, v, 1867, p. 365. 

 Description of genus: 



1. Body-form resembling that of the living Neoceratodus. 



2. Head covered with numerous plates, of which one is a large median 



occipital; a smaller median plate in front of it. 



3. Scales large, thin, irregularly ovate, or polygonal with rounded angles. 



4. Scales and external bones without a layer of ganoine. 



5. Dental plates, triangular, irregularly ovate, with few radiating ridges, 



which may be smooth, or more or less crenulated or denticulated. 



6. Caudal, continuous with dorsal and anal fins. 



Sf genodus dialophus (Cope). (Plate 26, figs. 6, 7.) 



1878. Ctenodus dialophus Cope, Proc. Amer. Philos. Soc, xvii, p. 528. 



1881. Ctenodus dialophus Cope, Amer. Nat., xv, p. 162. 



1888. Ctenodus dialophus Cope, Trans. Amer. Philos. Soc, xvi, p. 285. 



1891. Sagenodus dialophus (Cope), Woodward, Cat. Fos. Fishes, Brit. Mus., 11, p. 261. 



1899. Sagenodus dialophus (Cope), Williston, Kans. Univ. Quart., Ser. A. viii, p. 176. 



Type: Left lower dental plate lacking portions of first two ridges. 

 No. 7234 Am. Mus. Cope Collection. Texas. 



Referred specimen: An imperfect dental plate ; Texas. No. 7470 Am. Mus. 

 Original description: Dental plate "of narrow form, and has more num- 

 erous crests than any other known American species. They number ten, 

 and there are two or three other rudimental ones at the posterior extremity. 

 They are all more transverse than usual, five being directed forwards and five 

 slightly backwards. The crests are acute, but the grooves and emargina- 

 tions are not very deep. The crests are entire, except at the obliquely truncate 

 distal extremities, where there are from two to four dentations. The shining 

 layer does not extend within these. The inner border of the tooth is vertical, 

 excepting posteriorly, where the inner border of the crest-bearing portion 

 turns outwards, leaving a narrow ledge of the palatal face. The latter is 

 concave in cross-section. 



"Measurements. m 



"Length (0.004 at one end inferential) 0.033 



Width at fifth crest oio 



Depth opposite fifth crest C04" 



Sagenodus fossatus (Cope). (Plate 26, figs. 8-1 1.) 



1877. Ctenodus fossatus Cope, Proc Amer. Philos. Soc, xvii, p. 53. 



1877. Ctenodus gurleyanus Cope, Proc Amer. Philos. Soc, xvii, p. 54. 



1878. Ctenodus porrectus Cope, Proc Amer. Philos. Soc, xvii, p. 527. 

 1883. Ctenodus vabasensis Cope, Proc. Acad. Nat. Sci. Phila., p. no. 



Type: An imperfect, immature, left mandibular plate. No. 6506 Uni- 

 versity of Chicago Gurley Collection. Vermilion County, Illinois. 

 Referred specimens: 



1. The type of Ctenodus gurleyanus Cope — an upper dental plate. 



Vermilion County, Illinois. No. 6509 University of Chicago. 



2. Type of Ctenodus porrectus Cope — a lower (?) dental plate. 



Vermilion County, Illinois. No. 7235 American Museum._ 



3. Type of Ctenodus vabasensis Cope — one dental plate. Vermilion 



County, Illinois. No. 6510 University of Chicago, 



