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Page 2

FrtmJisPieee.- Head of DnUCHTHVS INTERMEDIUS, NEWBP:.IUlY, in front
and side vieW's. X h. From photograph of specimen collected by Dr. William
Clark, in the Waverly CLower Carboniferous) of Ohio, now in the collection of
Columbia College, New York. (V. p. 133·)

Page 156

TELEOSTO,lfES

Such in outline are
the essential structures
of a Teleost. They may
now be briefly con-
trasted with the morc
important characters of

,_..-

the Ganoids.
In skeletal structures

the Perch (Fig. 146)
may be strikingly con-
trasted with the most
nearly ancestral form
of Ganoid (Fig. 147).
In this, Polypterus (p.
148), the skeleton re-
tains a semi-calcified
condition. Its verte-
bral centra are practi-
cally separate from the
arches j its ribs, R, are
equivalent to the trans-
verse processes; its ac-
cessory ribs, AR, to
the "ribs" of Teleosts.
The cartilaginous brain
case is notably re-
tained; the membrane,
or dermal bones, of the
head roof, as I·; P, SP,
PO, 0, are clearly
scale -like, with an
enamelled surface, sim-
ilar in character to

Page 157

CANOIDS AND TELEOSTS 145

I
~f Dipterus. The shoulder girdle includes outer
dermal elements, DSG. The external parts of the 'mpaired
fins are dermal; but their cartilaginous supports are re-
tained, RB, even in the tail region. The caudal fin may
be regarded as either diphycercal or heterocercal. The
exposed parts of the paired fins, it is especially interesting
to note, are only in part dermal; the two rows of carti-
laginous supports are retained in a condition very similar
to that of sharks, R B; * two of the basal elements of the
pectoral fin, however, have retained the rod·like form in
strengthening the front and hinder margin of the fin.

In visceral structures the G:anoicls exhibit the fo~­
lowing noteworthy characters: a greater number of gill
arches; a spiracle; a short and almost straight digestive
tube, with spiral valved intestine; a shark-like pancreas;
an arterial cone, with many rows of valves; a cellular air-
bladder, like that of a Dipnoan ; primitive conditions in the
urinogenital apparatus; shark-like characters in the ner-
vous system and sense organs; a chiasma of the optic
nerves, (pp. 260-279).

Relationships and Descent

Johannes Muller, when separating Ganoids from Tele-
osts, recognized clearly even at that early date (r844) that
the majority of the structural differen<;es of these forms.
were bridged over in exceptional insfances; there were
thus Teleosts with bony body plates, as well as, it was
afterwards found, a Ganoid (Amia, p. r63) with herring-
like cycloidal scales. But he believed that three structural
characters of the Ganoids separated them constantly from
all Teleosts, and warranted the integrity of the groups.

• Contrast Gegenbaur's view that this fin represents the simplest known
condition of the arcbipterygium. Ref. on p. l48.

L

Page 312

INDEX

Wilson, H. V., 208.
Woodward, A. S., 8, 10, 24, 25, 33,

42, 66, 68-71, 80, 81, 106, 107,
112, 121, 127, 129, 131, 132, 135,
136, 146, 151, 154, 161, 164, 165;
phylogenetic table, compared, 282.

'Yorks on the general subject, fishes,
231-234; on the Cyclostomes, 234-
238; on the Ostracoderms and
Pa/tEospoltdylus, 238; on the sharks,
238-244; on the Chimreroids, 244;
on the lung·fishes, 244-246; on the

Ganoids, 246-249; on the Teleo5ts,
249-251•

_'(~lIacalJthlls, pectoral fin of, 39, 40,
42 (Fig. 53), 45; v. Pleuracan-
thus.

Zittel, K. v., table of geological dis-
tribution of fishes, 9; quoted, 81,
82,104,124,157,158,164,165.

ZoOlogical Society, Proceedings of,
257 note.

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