134 
Pleurodus Rankinii. Agass. 
P. AFFiNis. Agass. 
I have nearly 200 teeth of Pleurodus from the Bone-bed. 
They differ ver}^ much in form, size, and character ; some 
have broad, wing-like processes spreading from the main 
ridge of the tooth ; others narrow and elongated ; many are 
ornamented by a series of well-defined strise running across 
them transversely; whilst the majority are smooth and plain, 
or slightly punctured. The size ranges from two-tenths of 
an inch to seven-tenths. I think it is more probable that 
the teeth are from different parts of the jaw of one species, 
than that there are two species. Professor Agassiz, who 
named them, did not describe the species, so that little is 
known of his reason for separating them into two species. 
Helodus simplex. Agass. 
Rare. Two or three teeth. 
Helodus sp.? 
Rare. Two teeth. 
Cladodus mirabilis. Agass. 
These are probably the teeth of Ctenacanthus hyboides. 
Pcecilodus sp.? 
Two teeth. 
Harpacodus sp.? 
Several teeth. 
Petalodus Hastingsi^. Owen. 
Single teeth. I^ot uncommon. 
Ctenoptychius apicalis. Agass. 
Teeth. Not uncommon. 
