484 On the Fossil Fishes of the Carboniferous Limestone Serves of Great Bratarn. 
which is simple and homogeneous in Petalodus, being divided into a variable num- 
ber of distinct root-like lobes or fangs. 
During the year 1858 Agassiz revised the Petalodonts in the Florence Court 
Collection, and in addition to confirming the determination of M‘Coy with respect 
to Polyrhizodus, he raised the species P. psittacinus, Ag., to form the type of a genus 
Petalorhynchus. 
In 1866, Messrs. Newberry and Worthen published the following synopsis of 
Petalodont genera (“ Geol. Survey of Illinois,” Vol. II., p. 31) :-— 
Family, Petalodontidee, Newb. and Worthen. 
“Teeth compressed, transversely elongated, crown with anterior and posterior 
surfaces enamelled, meeting above in a more or less acute-angled edge, bordered 
below by imbricating folds of enamel, which encircle the crown; anterior crown- 
face generally convex ; posterior concave; root more or less developed, sometimes 
large, sometimes nearly obsolete, bony, rough, tumid.” 
The family, Petalodontide, as defined by Messrs. Newberry and Worthen, 
comprises the following genera :— 
1. Petalodus—Owen. 
P. hastingsiee—Owen (type). 
2. Petalorhynchus—Agass. (gen. indet.) 
P. sagittatus—Agass. (type, sp. indet.) 
3. Ctenophychius—Agass. 
C. serratus—Owen (type). 
C. apicalis (Ag. indet.) (type). 
4, Antliodus—Newberry and Worthen. : 
A. mucronatus—Newberry and Worthen (type). 
5. Dactylodus—Newberry and Worthen. 
D. princeps.—Newberry and Worthen (type). 
6. Polyrhizodus—M‘Ooy. 
P. magnus—M ‘Coy (type). 
7. Chomatodus—Agass. 
C. linearis—Agass. (type). 
To the above must be added :— 
8. Ctenopetalus (Ag. indet.)—Davis. 
C. serratus (Ag. indet.)—Davis (type). 
9. Harpacodus (Ag. indet.)—Davis. 
H. dentatus (Ag. indet.)—Davis (type). 
