480 



SCANDINAVIAN FISHES. 



pen, changed it to Gadus or/af. So close is the con- 

 nexion Ijetween this species and Gadus calhirius tliat 

 most recent writers have identified it with the latter. 

 Dressel", however, refers us to his measurements of four 

 specimens of G. ognc and the same number of G. cal- 

 Jdrias, and gives the following specific chai-acters: in 

 G. ogac the peduncle of the tail is shallower, the eyes 

 and the interorbital space larger, the barbel longer, the 

 ventral fins set farther forward, and the pectoral fins 

 longer, than in G. caUarias. 



The Dicksonian expeditions to Greenland have pat 

 the Royal Museum in possession of four specimens of 

 Gadus ngac, between 294 and 566 mm. long, which 

 show that most of the characters given I)y Dhessel lose 

 their validity when compared with the numerous changes 

 of growth in Gadus callar'uis. One of these characters, 

 however, that which is drawn from the relative breadth 

 of the interorbital space, and is adopted in our table 

 for the distinction of the species within this genus, has 

 proved universally true. This chai'acter, as well as the 

 difference that appears in the average position of the 



ventral fins, is of great interest in our fauna, for, though 

 the Baltic Cod never attains (juite the same point as 

 ogac in this respect, still it comes much nearer the 

 latter, on an average, than tlie oceanic Cod does. 



In the Cod the breadth of the interorbital space 

 increases even relatively during growth, rising in pro- 

 portion to the length of the body, according to our 

 measurements of Cod from the Cattegat and Skager 

 Rack, from 5'9 % in specimens on an average 142 mm. 

 long to 6'9 % in specimens on an average 462 mm. 

 long. In the Baltic Cod tliat we liave measured, the 

 latter percentage appears in specimens of an average 

 length of 422 mm., and in our specimens of G. ogac, 

 of an average length of 435 mm., this proportion is on 

 an average 8'4 %. In this relation, however, the charac- 

 ter is not constant, for in inacrocephalic Cod the per- 

 centage may rise to at least 9; but it becomes constant 

 if we compare the breadtli of the interorbital space with 

 the length of the head, when we obtain the following 

 average results: 



In accordance with the general rule for the changes 

 of growth of the Teleosts, that the ventral fins move 

 more and more forward, the distance between the fore- 

 most (outermost) point of the insertions of these fins 

 and the beginning of the first anal fin shows a per- 

 sistent increase during growth in the Cods, when com- 



pai-ed with the length of the body. The length of the 

 base of the first anal fin also persistently decreases in 

 comparison witli the distance between this fin and the 

 ventral fins. In these respects too, Gadus ogac is most 

 advanced in development, though the Baltic Cod show 

 a distinct tendency towards the same point. 



In Cod from the Cattegat and Skager Rack . 



Bultie 



„ Gadus ogac 



Average length 



of the body 



in mm. 



89.4 

 l'J2.o 

 408.3 

 422.0 

 434.5 



Average length of 

 the base of the first 

 anal fin in ?^ of the 



distanec from the 



insertions of the 



... „ . ... ventral tins to the 



anal nn in % ol the ... „ ,, 



1 .u /• .1 u J ' l)e!;inning ot the 

 length of the bodv. ^ . ^ , ^ 

 first anal hn. 



Average distance 

 between the inser- 

 tions of the ventral 



fins and the be- 

 i;Inning of the first 

 anal fin in °i of the 



19.2 

 21.2 



24.1 

 2(j.i 

 29,7 



93.9 

 91.1 

 74.8 

 74.2 

 G2.3 



" Pnic. U. S. Nat. Mus., vol. VII, p. 246. 



