THE EOCENE PERIOD. 295 
been found in any Tertiary stratum; but the internal skeletons 
of Cuttle-fishes (such as 4elosepia) are not unknown. 
Remains of /zshes are very abundant in strata of Eocene 
age, especially in certain localities. The most famous depot 
for the fossil fishes of this period is the hmestone of Monte 
Bolca, near Verona, which is interstratified with beds of vol- 
caric ashes, the whole being referable to the Middle Eocene. 
The fishes here seem to have been suddenly destroyed by a 
volcanic eruption, and are found in vast numbers. Agassiz 
has described over one hundred and thirty species of Fishes 
from this locality, belonging to seventy-seven genera. All 
the species are extinct; but about one-half of the gevera are 
represented by living forms. The great majority of the 
Fig. 223.—Rhombus minimus, a small fossil Turbot from the Eocene Tertiary, 
Monte Bolca. 
Eocene Fishes belong to the order of the “ Bony Fishes” 
( Zeleosteans), so that in the main the forms of. Fishes charac- 
terising the Eocene are similar to those which predominate 
in existing seas. In addition to the above, a few Gavoids and 
a large number of P/acoids are known to occur in the Eocene 
rocks. Amongst the latter are found numerous teeth of true 
Sharks, such as Ofodus (fig. 224) and Carcharodon. The 
pointed and serrated teeth of the latter sometimes attain a 
length of over half a foot, indicating that these predaceous 
fishes attained gigantic dimensions; and it is interesting to 
note that teeth, in external appearance very similar to those 
of the early Tertiary genus Carcharodon, have been dredged 
from great depths during the recent expedition of the Chal- 
lenger. There also occur not uncommonly the flattened 
