462 Trans. Acad. Sci. of St. Louis. 



VERTEBRATA. 

 PISCES. 



PtTCTODUS EA8TMANI D. sp. 



Plate l,Jig$. 31^32. 



Occasional abraded tritors of a species of Ptyctodus occur 

 in the Glen Park limestone, and one nearly perfect specimen 

 of a complete dental plate has been observed. The abraided 

 specimens are indistinguishable from similar specimens of P. 

 calcpoltts N. & W., found in the Devonian at many localities 

 in the Mississippi valley, but the complete specimen preserves 

 characters which distmguish it from that species as it has 

 been illustrated by Eastman.* The most notable character- 

 istic of the Glen Park species as distinguished from P. cal- 

 ceoluSj is in the lower margin of the tooth, this margin de- 

 scribing a continuous slightly concave curve from the pos- 

 terior to the anterior extremities, while in P. calceolus this 

 margin is convex from the posterior extremity to a conspicu- 

 ous sinus below the anterior extremity of the tritor, and then 

 convex again nearly to the anterior extremity of the sym- 

 physial beak where there is a conspicuous downward extension 

 of the tooth. The upper surface also differs from P. cal- 

 ceolus in having a less conspicuous differentiation between 

 the tritorial and the symphysial regions. 



The Glen Park species is named in honor of Dr. C. R. 

 Eastman, who has done so much valuable work upon the 

 Paleozoic fishes. 



Conclusion. 



A critical analysis of the Glen Park fauna brings out several 

 features of great interest. A study of its relationships to 

 other faunas shows it to be allied in two directions, on the 

 one hand to the faunas of the Hamilton formation of the east, 

 giving it a strong Devonian aspect, and on the other hand 

 with the Kinderhook faunas of the Chouteau limestone and 

 associated formations in Missouri and elsewhere. Although 

 most of the species appear to be distinct from their Hamilton 



♦ Iowa Geol. Sarv., vol. 7, p. 115; Am. Nat., vol. 82, p. 477. 



