2429 FOSSIL REMAINS OF HYBODUS 
Art. IX.—Illustrated Zoological. Notices. By Enwarp CHaRis- 
wortH, E.G.S., &c. 
(Continued from Vol. i. n. s. p. 534.) 
On the Fossil Remains of « Species of HYBODUS, from Lime Regis: 
Our, acquaintance, with, the zoological, history of the defen- 
sive, fin-bones. termed, Ichthyodorulites, both as. it respects 
their specific determination and the group, of fishes to which 
they appertain, is principally due. to; the labours. of Louis 
Agassiz.: and.a.considerable, portion, of the..work now in 
course of publication, by this eminent naturalist,—the ‘Re- 
cherches surles, Poissons: Fossils,—is. devoted to the illus- 
tration. and, description of these interesting fossils... Ranging 
vertically; fromthe, deposits of the, cretaceous period to those 
of the Silurian, system, and horizontally throughont. an area 
of probably unlimited extent; the, Ichthyodorulites, owing to 
their bony texture,and exterior of enamel, have been presery- 
ed during the long period, of, theiz,entombment with singular 
fidelity ; and when disinterred, from their matrix, assisted, by a 
knowledge of the teeth, with which these osseous rays were 
formerly associated, the, ichthyologist..may safely venture, to 
infer their relation. to existing types, though all other traces 
of the skeleton may, have disappeared. 
The genus Hybodus.is spoken of by Agassiz as being. per- 
haps the most important of, the extinct genera of placoid, or 
cartilaginous. fishes, in. which, one or, both dorsal fins were 
armed with these, defensive weapons. A large, number of 
species are already characterised in the ‘Poissons Fossils,’ 
