VEKTEBRATES. 33 



3. Genus CTENOPTYCHIUS, Ag. 



Teeth small; crown as in Petalodus, but upper margin serrate, 

 crenulate or dentate; root oblong, rounded, entire. 



Ct. seriatus, Owen (type). Sub-carboniferous, Europe. 



Ct. apicalus, Ag. Sub-carboniferous, Europe. 



Ct. semicircular is, N. and W. Coal Measures, Indiana. 



4. Genus ANTLIODUS, N. and W. 



Teeth transversely elliptical, compressed, concavo-convex ; 

 crown similar to that of Petalodus; root sliort or obsolete. 



A. mucronatus, N. and W. Sub-carboniferous, Illinois. 



A. pai'vulus, N. and W. Sub-carboniferous, Illinois. 



A. similis, N. and W. Sub-carboniferous, Illinois. 



A. cucidlus, N. and W. Sub-carboniferous, Illinois. 



A. politics, N. and W. Sub-carboniferous, Illinois. 



A. minutus, N. and W. Sub-carboniierous, Illinois. 



A. simplex, N. and W. Sub-carboniferous, Illinois. 



A. stdcatus, N. and W. Sub-carboniferous, Illinois. 



A. robustus, N, and W. Sub-carboniferous, Illinois. 



Probably Chomatodus truncatus, Ag., {McCoy Brit. Palceoz. 

 Foss., p. 618, pi. 3c, fig. 1) and Chom. linearis, Ag., the speci- 

 men figured Poiss. Foss. Atlas, pi. 12, fig. 5, shoukibe included 

 in this genus. 



5. Genus DACTYLODUS, N. and W. 



Crown as in Petalodus; root conspicuous and divided into a 

 number of radicles. 



D. princeps, N. and W., (type). Sub-carboniferous, Illinois. 

 D. lobatus, N. and W. Sub-carboniferous, Illinois. 

 I), infiexus, N. and W. Sub-carboniferous, Illinois. 

 —5 



