484 
SCANDINAVIAN FISHES. 
In the tii'st relation, the length of the snout in 
proportion to the postorbital length of the head, the 
direction of development differs in the two forms, and 
thus indicates a true specific distinction. In the other 
relations the direction of development is the same, but 
the difference between the percentages in both forms is 
considerable enough — in c and cl at least — to be em- 
ployed as a specific distinction. For all this, the forms 
are so like each other that one may well be tempted, 
remembering the dubious value in the Cods of the 
characters drawn from the coloration, to explain ivaclmja 
as a short-nosed form, which is, however, more ad- 
vanced in development, of the same species as navaga , 
which is apparently always inferior in size to waclmja a . 
The fin-formula may be regarded as identical in both 
forms, though here, as in several other Gadoid species, 
we find the peculiarity that in many cases the larger 
specimens have fewer rays in one or more of the fins * * 6 . 
Another Arctic species, Gadus saida 1 ', the Polar j 
Cod ( Gadus polaris) of later authors, comes very near 
navaga , but is one of the species that have best claim 
to the rank of a, distinct subgenusC It has never been 
found alive on the coasts of Scandinavia, but occurs 
pretty often in our Glacial clays, and has thus at no 
very distant period, geologically speaking, belonged to 
the fauna of Sweden and Norway (fig. 121). 
The most distinctive characters of the Polar Cod 
lie in the rapid attenuation of the hind part of the 
body; the rather forked shape of the caudal fin; the 
comparatively great distance (as in Gadus navaga) be- 
tween all the vertical fins, the length of the base of 
the third dorsal fin being at least equal to that of the 
second dorsal fin; the long paired fins, of which the 
pectoral fins have the middle rays longest or only 
slightly shorter than those immediately above them, 
the great length of the ventral fins being due, as usual, 
to the filamentous elongation of the second ray; the 
large eyes; and the prominence (though sometimes only 
slight) of the lower jaw. Most writers have been in- 
duced by the last character to range the Polar Cod next 
to the Coalfish-group; but the character is present, 
though only slightly appreciable, in the youngest stages 
of the Common Cod, and the resemblance between the 
Polar Cod and navaga is too great to admit of any 
remote separation of these two forms. Again, by the 
comparatively small number of rays in the first dorsal 
fin the Polar Cod is incontestably referred to the group 
of the true Cods 6 . The following table is calculated 
a According to Pallas navaija is generally about 7 1 / in. long ( spitliamalis ), wachnja 15 in. ( bispitliamalis ). The specimen of navaga 
measured by KOlreuter was, however, 283 mm. ( 1 1 ■ 2 in.) long. 
6 Gadus navaga: D. 1 3 1 1 7 -20|21— 24; A. 21—24(21—22; P. 19 — 20; V. 6; C. x + 25+x. 
„ gracilis: „ 12 — 1 3 1 G — 19(20 — 21; ,, 21—23(20—21; „ 19 ; „ 6; „ x + 23—27+x. 
c Gaclus saida , Lepechin, N. Comm. Acad. Petropol., tom. XVIII (1773), p. 512, tab. V; Pall., Zoogr. R. Asiat., tom. Ill, p. 199; 
Coll., N. Nordb.-exped., Zool., Fiske, p. 126, pi. IV, fig. 33; Bean ( Boreogadus , ex Gthr), Proc. U. S. Nat. Mus., vol. IV (1881), p. 243 ; 
Joud., Gilb., Bull. U. S. Nat. Mus., No. 16, p. 807: Turner, Nat. Ilist. Alaska , p. 89, pi. II; Lilt.j. (Gadus), Bv., Norg. Fn., Fisk., vol. 
2, p. 103. Gadus ceglefinas, Fabr., Fn. Groenl., p. 142. Merlcingus polaris, Sab., Sup pi. App. Parry’s First Voy ., p. 211; Richards., 
Fn. Bor. Amer., part. Ill, p. 247; Nilss., Skand. Fn., Fisk., p. 969; Gill. (Boreogadus), Proc. Acad. Nat. Sc. Philad. 1863, p. 233; 
Mgrn, Ofvers. Vet.-Akad. Forh. 1864, p. 531. Gadus Fabricii, Richards., 1. c., p. 245. Gaclus agilis, Rhdt, D. Vid. Selslc. Math. Naturv. 
Afh., Deel 7, pp. 115 et 126; Nilss., 1. c., p. 568. Gadus glacialis, Peters, Zw. Deutsche Nordpolarfalirt, Bd. 2, p. 172. 
d Boreogadus, Gthr, Cat. Brit. 71 fits., Fish., vol. IV, p. 336. 
e In Gadus saicla the fin-formula according to our investigations is: D. 12 — 1 3 1 1 4 — 18(18 — 22; A. 15 — 19(19 — 22; P. 18 — 19; 
V. 6; C. .v + 20— 22 + x. 
