l66 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



Genus CERATODUS Agassiz. 

 Poiss, Fos., Ill, 1838, p. 129. 



Revised description of genus: 



1. Body-form similar to that of the living Neoceratodus. 



2. Head with relatively few, thin bones; two ("ethmoid" and "occip- 



ital") in the median line, one behind the other; three pairs of 

 lateral plates symmetrically disposed on either side of these. 



3. Scales large and thin. 



4. Paired fins, archipterygia with biserial radials, and covered with 



scales. 



5. Dental elements irregularly triangular, with ridges developed into 



stout cusps, without lateral denticles. 



Ceratodus favosus Cope. (Plate 27, figs. 11, iia.) 



1884. Ceratodus favosus Cope, Proc. Amer. Philos. Soc, xxii, p. 28. 



1888. Ceratodus favosus Cope, Trans. Amer. Philos. Soc, xvi, p. 286. 



1891. Ceratodus favosus Cope, Woodward, Cat. Fos. Fishes, Brit. Mus., 11, p. 274. 



1908. Ceratodus favosus Cope, Hussakof, Bull. Amer. Mus. Nat. Hist., xxv, p. 51, 



Type: A fragment of a splenial with portion of a dental element show- 

 ing two cusps. No. 7230 Am. Mus. Cope Collection. Texas. 



In the writer's opinion the type of this species was too fragmentary for 

 specific description. Its distinctive characters are given by Cope as follows: 



Original description: "The species may be distinguished from those 

 described by Agassiz, and from the existing species, by the great depth of 

 the two emarginations of the external side. These enter the crown so deeply 

 as to reduce its width to dimensions no greater than those of each of the 

 processes of the crown. The internal face is strongly convex, and one 

 extremity is more strongly recurved than the other." 



The first of these two supposedly distinctive characters applies equally 

 well to some dental elements of Neoceratodus forsteri. In fact I have a 

 dentition of this species before me in which the emarginations are certainly 

 as deep as in the type of C. favosus. And as to the second character, 

 namely, that "the internal face is strongly convex, and one extremity is 

 more strongly recurved than the other" — that I believe will apply equally 

 well to many other ceratodont dental plates. The convexity of the internal 

 face in these dental elements is quite variable. All that should have been 

 concluded from the specimen was the presence of Ceratodus in the Permian 

 of America; but no new species should have been founded upon it. How- 

 ever, since the species has been established, we have no alternative but to 

 retain it until better material comes to light and proves it either valid or 

 merely a synonym. 



Genus GNATHORHIZA Cope, 

 Proc. Amer. Philos. Soc, xx, 1883, p. 629. 



The genus Gnathorhiza was founded by Cope on small dental elements 

 which he thought "very doubtfully * * * may belong to the Petalo- 

 dont family." Since the date of his description, however, several similar 

 elements have been discovered, and from these it is quite certain that they 

 represent the dental system of a dipnoan and not of a shark. This dipnoan, 

 as far as one may infer from the dental plates alone, differed strongly from 

 all others and should stand as generically distinct. 



