24 
SCANDINAVIAN FISHES. 
observations, that during the development of some of 
the Acanthopterygians there occurs a juvenile period 
which reminds us of the Ganoid type. As instances of 
this we may give the Tholichthys stage of the Chcetodon 
family", the Cephalacanthus stage of the Swordfish 6 , and 
the Bhynchichtys stage for the Berycides The latter, 
however, as they are included in the great series of the 
Percomorph families, are themselves to be regarded as 
similar mementoes. With this point also is connected 
the denticulation of the preoperculum d which appears 
during youth and subsequently disappears, in many forms 
of the great Scomberomorph series. In these common 
traces of an older type lies a band of union, which ex- 
plains the difficulty of finding concise expressions of the 
family characters and of referring them to natural groups. 
Where the history of development has not yet taught 
us anything as to the natural relationship of the families 
to each other, there remains nothing, except to allow iso- 
lated characters to decide the point, though they may per- 
haps lead us to construct a more or less unnatural system. 
According to the precedent set by Gunther* 1 , but 
with those alterations which seem to be rendered neces- 
sary by the attempts of later writers 7 to systematize, 
we shall arrange the families of the Scandinavian Fauna 
that belong to this division, in accordance with the views 
that seem to us the most natural. The Acanthopterygii 
Lysipharyngei seem to us most naturally suited for a 
primary classification in two great divisions, limited 
according to the structure of the caudal and paired fins. 
Among the latter, the ventral fins vary in situation and 
in composition; and the pectoral exhibit a considerable 
difference in breadth, a difference which also affects the 
shape of the basal bones of these fins. Besides these 
differences, there is also in most cases a difference in 
the composition of the caudal fin, most easily expressed 
in the number of the branched rays of this fin. In 
those Lysipharyngei which in most other respects are 
the most regular, the ventral fins are placed below the 
pectoral, or just behind the perpendicular from the base 
of the latter fins ( Acanthopterygii tlioracici ), and consist 
most often of one spinous ray and five soft rays. The 
pectoral fins are comparatively narrow (Ac. stenobrachii), 
and the basal bones generally narrow and shaped like 
a sand-glass: the number of branched rays in the caudal 
fin is comparatively larger (Ac. euryripidi). This divi- 
sion of Lysipharyngei may be called Idiopteri 9 on ac- 
count of the regularity of the structure of their fins. The 
second division may also, it is true, possess thoracic and 
regular ventral fins. But most commonly these fins 
have fewer rays, are changed into organs of walking or 
adhesion, or situated on the abdomen (Ac. abdominales) 
at some distance behind the pectoral fins, or sometimes 
before the latter on the throat (Ac. jugular es). The pecto- 
rals are generally broad at the base, or their basal bones 
at least are broad and flat (Ac. eurybrachii ) or abnorm- 1 
ally developed in some other way (pediculati). The caudal 
fin has fewer branched rays*, generally less than 15 (Ac. 
stenoripidi). This division we shall call Anonial opteri 1 . | 
In addition to the characters of these divisons which 
we have now described, there also exists a biological 
difference between them. The first division contains, 
generally speaking, fishes of an active way of life, whether 
they be shore-fishes, wandering pelagic fishes, or deep- 
sea fishes. The second division includes, on the con- 
trary, bottom-fishes of a more quiet and sluggish way 
of life. The more marked this way of life is, the more 
distinctly do these characters appear; and if the mode 
of life be changed, there may generally be observed, 
both in the shape of the body and in the other characters, 
an apparent transition in the direction of the other type. 
The types around which most of the other Idiopteri 
may most conveniently be arranged in families are, in the 
Scandinavian Fauna, the Perch and the Mackerel, which 
may therefore each give their names to one of the series 
here described, series which, from a systematical point 
of view, are correlative to that of the Pharyngognathi. 
Lutken, Spol., Tab. II, fig. 11. 
a Lutken, Spot. tab. V, fig. 7 — 11. 
6 Gunther, Journ. Mus. Geoft’r., Bd. I, p. 170 (Heft. 2, p. 98); 
c Lutken, Spol., Tab. II, fig. 4 — 7. 
d Lutken, Spol., Tab. Ill and IV. 
e Brit. Mus. Cat., Fish., Systematic Synopsis of Acanthopt. Fish. (App. to Vol. Ill) and An Introd. to the Study of Fishes, p. 374, 
Handb. d. Iehth., pp. 263 etc. 
f Cope, Contr. to the Iehth. of the Lesser Antilles, Trans. Am. Phil. Soc.. Vol. XIV, n. ser., Art. V, p. 445. — Fitzinger, Vers, 
einer Naturl. Classif. d. Fische, Sitzber. Akad. Wiss. Wien, Math. Naturv. Cl., Bd. LXVII, Abth. 1, p. 5. — Gill, Arran g. Fain, of Fishes, 
Smiths. Misc. Coll., vol. XI, Art. 11 (n:o 247). — Jordan & Gilbert, Syn. Fish. N. Am., Bull. U. S. Nat.. Mus. n:o 16. 
g Orthocormi thoracopteri (p. p.) Fitzinger, 1. c., p. 28. 
h Such exceptions as Gobius lanceolatus, for instance, clearly depend upon the fact that the supporting rays of the caudal fin (at the 
top and bottom) are also branched. 
1 Orthocormi pseudogastropteri (p. p.) + Heterocormi acanthopteri 4- Anomali pediculati, Fitz. 1. c. pp. 34, 39, 48. 
