SALMONS AND CHARRS. 
839 
and S. trutta. Now hybridism does not- necessarily in- 
volve sterility; and with regard to the Silver Salmon 
and similar forms, it may well be difficult to determine 
in each case whether it is an altered manner of life — 
a longer stay in the sea or large lakes — or hybridism 
that has brought about the said changes of form. But 
it appears to be demonstrated that these changes attend 
either or both of the above conditions. 
In Sweden and, generally speaking, in all temperate 
countries, the Charrs are true fresh-water fishes; but 
such is not the case in the arctic parts of their geo- 
graphical range. There they live like the Salmon; Es- 
mark a and Hetting 6 found them in the Arctic Ocean 
off Norwegian Finnmark, and off Spitsbergen they are 
the favourite food of the Beluga (Delphinapterus lencas), 
which follows them to the head of the gulfs and bays. 
In the sea they wear the colours of Silver Salmon, 
and do not acquire their proper Charr dress before 
entering the rivers. 
Characters both of form and colour indicate in 
their variations a close relationship between the Sal- 
mons. Their differentiation seems to be of late origin, 
and they should perhaps be regarded as species which 
are still developing constancy of characters c . 
The skeleton of the Salmons is feebly ossified in 
sharp contrast to that of the preceding family. The 
cranium is for the most part persistently cartilaginous, 
and most of its bones lie as separate covering-bones 
on the almost continuous capsule of cartilage. The 
occipital ridge is merely a short terete process, extend- 
ing about as far back as the ordinary processes from 
the mastoid (epiotic) and squamose (pterotic) bones. 
The posterior oculo-inuscular canal is large, and pe- 
netrates the occipital region behind, being covered 
below by the parasphenoid bone, which is strongly 
bent in the sphenoidal region, and centrally divided 
in front by the Y-shaped ba.sisphenoid bone, which is 
wanting in the preceding family. Here, on the other 
hand, as in the following genera, there is no pha- 
ryngeal process. The orbits are separated internally 
by a thick wall, composed of cartilage and the orbito- 
sphenoid bones. The osseous framework of the upper 
jaw, as we have mentioned above, is quite different 
from the corresponding structure in the Cyprinoids. 
The maxillaries articulate in front, like the intermaxil- 
laries and the palatine bones, and close between these 
two pairs, with the cartilaginous rostral part of the 
cranium (the rostro-ethmoidal cartilage). But they 
have undergone considerable elongation — the inter- 
maxillaries, on the other hand, are comparatively short 
— and are furnished with teeth, as well as the inter- 
maxillaries and the palatine bones. Their anterior part 
is, however, covered below by the intermaxillaries, so 
that their externally visible length — as it is given in 
the above definition of the genus — is measured from 
the hind extremity of the latter bones. Above their 
posterior part lies the covering-bone (os supplement, are ) 
which answers to the cheek-bone (os jugate) of the 
higher vertebrates. The vomer is set as a covering- 
bone on the middle of the under surface of the rostro- 
ethmoidal cartilage and on the anterior extremity of 
the parasphenoid bone. In the Salmons its shaft (body) 
is fairly long and broad, earinated on the under (outer) 
surface, but thin; in the Scandinavian Charrs, on the 
other hand, ossified hardly at all or only on the sides. 
The dentition of the vomer is also confined, as a rule, 
in the latter to the anterior part, the so-called head; 
while in the Salmons it extends, at least during youth, 
to the shaft as well, but is generally more and more 
reduced with age. The other bones of the palate, ex- 
cept the palatine bones proper, are toothless in this 
genus. The pterygoid bones are slender and curved in 
the ordinary manner to unite the palatine and quadrate 
bones. Within them lie the mesopterygoid bones, which 
are thin, but broad behind, and form the greater part 
of the roof of the mouth. According to Lilljeborg 
these two bones afford a constant distinction between 
Trout and Salmon. In the former, he says, their breadth 
decreases from their middle point even in a backward 
direction, whereas in the latter they grow broader all 
the way from the anterior to the posterior extremity. 
A great difference from the preceding family appears 
in the branchiostegal membranes, which are fur- 
nished with a far greater number of rays (9 — 12, in 
exceptional cases 8 or as many as 14, in Oncorhyn- 
chus sometimes 16). These rays are, however, of the 
same broad, blunt, sabre-like form as in the Cy- 
prinoids. 
a Skand. Naturf. Mode, Chrnia 1868, Forh., p. 527. 
b Smitt, 1. c., tab. metr. VI, No. 399. 
c “In numerous cases one is much tempted to ask whether we have not to deal with a family which, being one of the most recent 
creation, is composed of forms not yet specifically differentiated”: Gunther, Cat. Brit. Mus., Fish., vol. VI, p. V (preface). 
106 
Scandinavian Fishes. 
