PHYSOSTOMES. 
689 
TBLEOSTEI PHYSOSTOMI. 
Osseous fishes with the air-bladder (if present) furnished with pneumatic duct. Ventral fins (if present) ab- 
dominal. No spinous rays proper (unarticulated) in the fins". 
Each of these three characters calls to mind an 
era in the history of ichthyology. The last was ArtediV 
character of the order Malacopterygii (pinnis inermibus); 
it was by the second that Linnjeus 6 defined the order 
Abdominales (pi nine ventrales pone pinnas pectorales); 
and the first-mentioned character was Muller’s'* ex- 
pedient for the better definition of Malacopterygiens 
abdominaux, the order which Cuvier 6 had adopted in 
his system, and for the combination therewith of Cu- 
vier’s Malacopterygiens apodes. 
The order or rather suborder which has thus arisen, 
is hardly more natural than that of the Physoclysts, 
just as the whole Teleosteous order is merely an ex- 
pression of the community of those characters which 
the fishes belonging to the several directions of deve- 
lopment of this type have retained or acquired during 
their development from a common prototype, the Ga- 
noids. The independence of the directions of develop- 
ment asserts itself everywhere, and the characters of the 
system must therefore be employed with discrimination. 
The Physostomes in general stand nearer the Ga- 
noids, which were probably also furnished with a pneu- 
matic duct from the air-bladder. This connexion with 
the Ganoids appears in the abdominal position of the 
ventral tins, which have besides retained not unfrequently 
a greater number of rays, just, as the pectoral fins may 
display more numerous transverse rows of basal bones, 
though the outer (distal) rows are not ossified 7 . An- 
other sign of this connexion is given by the exceptions 
which occur in certain Physostomes, to the character 
that, otherwise distinguishes the Teleosts with regard 
a The rays which in these fishes are termed spines, as being 
ture, being - articulated, although the joints are coalesced. 
b Gen. Pise., p. 1. 
to the structure of the arterial bulb of the heart, a 
structure which in this suborder may be almost Ganoid. 
These resemblances to the Ganoids range the Physo- 
stomes lower in the system, assuming that the system 
should be an expression of the development. But for all 
this we must not regard the structure of the Physo- 
stomes as more primitive; many of them on the con- 
trary possess more highly developed organs than the 
corresponding organs in the Physoclysts. Among these 
organs we find, for example, the stronger supporting- 
apparatus which the pectoral fins have acquired in 
several Physostomes by the addition to the scapular 
disk of a special bone for this purpose (os prcecora- 
coideum a ). Another example of this is the far more 
frequent occurrence in the Physostomes than in the 
Physoclysts of the connexion between the air-bladder 
and the organs of hearing, a connexion which is ef- 
fected in several of them by a special chain of bones 7 '. 
The preponderant part of the Physostomes, as op- 
posed to the Physoclysts, is composed of fresh-water 
fishes; but the family most important among marine 
fishes in an economical respect, that of the Herrings, 
is Physostomous. This order also contains the families 
of the Salmons, Carps, Pikes, and Eels, all of which 
have been of great importance in human economy since 
time immemorial. 
The Physostomes are not so numerous as the Physo- 
clysts — we know about 1,900 species of the former, as 
opposed to 3,300 of the latter — but the distinction of 
form is sufficiently wide to require the establishment 
of several independent series which we here give prin- 
hard and stiff, show their Malacopterygian nature in their internal strue. 
c Syst. Nat., ed. X, tom. I, p. 241. Cuvier completed the Linniean character by the addition that the ventral fins not only lie be- 
hind the pectoral fins, but are also destitute of any immediate connexion with the shoulder-girdle. 
d Abh. Akad. Wiss. Berl. 1844, Phys. Abb., p. 175. 
e R'egne Animal , ed. 1, tom. II, p. 159; ed. 2, tom. II, p. 269. 
f Cf. Gegenbaur, Unters. Vergl. Anat. Wirbeltli., 2:te Heft, p. 153, taf. VIII, figg. 8 et 9. 
<J Prtecoracoid, Parker, Shoulder- girdle and Sternum , p. 56, pi. II, fig. 8, p. cr; Knochenspange, Gegenbaur, 1. c., p. 117, taf. VII, 
fi gg- 1 — 5, , v . 
h Sagemehl (Morphol. Jahrb., P>d. X, p. 22) gave these fishes the name of Ostariopliysete Teleosts, from oocagiov, a small hone, and 
fpvoa, bladder. 
