244. MM. Pictet and Humbert on the Fossil Fishes 
there are, however, the two principal types, Sharks and Rays. 
These fishes are for the most part difficult of comparison with 
other fossil species ; for, in most deposits, the Elasmobranchi are 
only indicated by isolated teeth : in the Lebanon, however, the 
case is quite different ; there are no isolated teeth, but some few 
entire bodies. 
‘The subclass of the Ganozds is, in all known faunas of the Cre- 
taceous period, in rapid course of extinction. This renders all 
the more interesting the fact that the faunas of the Upper Jura 
which immediately preceded this period are rich in numerous 
and fine characteristic species of this subclass. We have not 
found at Lebanon any true Ganoid; for we no longer retain in 
that subclass the order Hoplopleuridz established by one of our- 
selves. This order belongs properly to the great series of Te- 
leosteans. 
This third subclass is consequently by far the most important. 
It affords almost the total of the fauna, and it is with it that we 
have more particularly to deal at present. 
As we have said above, M. Agassiz did not place the existence 
of the Teleostei further back than the Cretaceous period; the 
greater number of authors now, however, recognize an exception to 
this rule, and regard as Teleosteans in all probability the genera 
Tharsis, Leptolepis, &c., with minute rounded scales. Taking 
for granted the correctness of this view, which it would take us 
too long to discuss here, we have to notice a very important 
fact, which is that the Teleostean fishes of which M. Agassiz 
forms his family Halécoides, and which we know under the 
names of Salmones and Clupea, are manifestly the nearest rela- 
tives of these same Jurassic genera. The numerous family to 
which these precious types of our present seas belong are actu- 
ally the descendants of the Jurassic Teleosteans. They have a 
history longer than that of any other existing family, and may 
be regarded as, in some sort, the trunk of the genealogical tree 
of the fishes of our present seas. 
It is, further, very interesting to find that these fishes are 
the ones which present developed in the highest extent the 
normal characters of their class, and that they thus in some 
sort represent the archetype thereof. A theoretical anatomist, 
wishing to set forth this archetype, would be inevitably led to 
depict a figure almost exactly like that of a Halecoid, since he 
would assign to it ventrals in the normal position far back on 
the abdomen, and a mouth with the edge composed of both 
maxillary and intermaxillary ; and nothing is more normal than 
the fins of a salmon and its regular and fusiform body. 
We may, then, assume that the most ancient Teleostean 
fishes were the most normal in their forms, and that their cha- 
