918 
SCANDINAVIAN FISHES. 
Espos. intern. Pesca, Berlin 1880, Sez. Ital., p. 102) + 
Arg. yarrelli, p. 418. 
Goniosoma argentinum, Costa, Fna Regn. Nap., Malacotterigii 
Abdominali, Genere Goniosoma, tab. XXXVI. 
Argentina decagon , Clarke, Trans., Proc. N. Zeal. Inst., vol. XI 
(1878), p. 295, tab. XIV, fig - , infer, (vide Day, 1. c.). 
(?) Argentina elongata, Hutton, Ann., Mag. Nat. Hist., ser. 5, 
vol. Ill, p. 53; G^chr, Deep Sea Fish., Chall. Exped., p. 
218, tab. LV, fig. B. 
The Hebridal Siil-Smelt attains at most about half 
the length of the preceding species". It is besides, in 
most cases, of a more elongated form, the greatest 
depth in adult specimens — with the exception of gra- 
vid females — being about 13 % of the length of the 
body; but in this respect there is no constant distinc- 
tion In other respects too both species are so like 
each other that the essential differences are but few. 
The Hebridal Siil-Smelt has a comparatively longer anal 
fin, a higher dorsal fin, smaller eyes and less developed 
adipose membrane on the head — it is no true deep- 
sea fish — fewer rays in the pectoral and ventral fins, 
fewer scales, vertebras, and gill-rakers, but a somewhat 
longer peduncle of the tail (behind the adipose and the 
anal fins). To these we should add a characteristic 
first remarked by Lilljeborg, the faint S-shaped cur- 
vature of the lower posterior margin of the operculum 
in the Hebridal Siil-Smelt. But in coloration this spe- 
cies differs widely from the Greater Siil-Smelt, owing 
to its thin and more silvery scales, most of them de- 
ciduous. 
The length of the head in adult specimens is some- 
what less than * 1 / i of that of the body, the longitudinal 
diameter of the eyes rather more than || 4 , and the 
postorbital length about 2 / 5 , of the length of the head. 
The forehead is flat, the supraorbital parts being hardly 
at all tumid, but their outer margins indented in a 
rounded manner above the middle of the eyes. The 
nostrils lie rather near to the orbits, and they are of 
fairly equal size, or the anterior is even a, little larger 
than the posterior. They are circular, or oblong in the 
longitudinal direction of the body. The breadth of the 
snout at the nostrils is perceptibly less than the width of 
the interorbital space, and its length is about equal to the 
longitudinal diameter of the eyes. The jaws are relati- 
vely somewhat shorter than in the Greater Siil-Smelt, 
the length of the maxillaries being about 19%, that of 
the lower jaw about 307 2 %, of the length of the head. 
The transverse row of palatine teeth is sharply defined 
at both ends, the margin of the palatine bones being 
indented just behind them. The gill-rakers are not 
only more scattered but also comparatively shorter 
than in the preceding species. The pseudobranchise 
are rather large here as there. 
The height of the dorsal fin is about equal to the 
length of the head reduced, or nearly 18 % of the 
length of the body, and perceptibly more than twice 
the length of the base of the fin. Here too the anal 
fin begins at the termination of the third quarter of 
the length af the body, but the length of its base is 
nearly 2 / 5 of that of the head. The adipose fin begins 
above the 2nd or 3rd branched ray in the anal. 
The pectoral fins, the length of which is about 
13 7 2 % of that of the body, are rather shorter, the 
ventrals, on the other hand, somewhat longer, than in 
the preceding species, the length of the latter being 
only about Vio Gss lhan that of the former. 
The form of the scales varies as in the preceding 
species, but their spines are less developed. 
In fresh specimens, according to Edward, the 
body is so transparent that on holding it up to the 
light the vertebra? can be distinguished. The divisions 
of the brain are even more distinctly visible through 
the parietal and frontal bones than in the preceding 
species. The back is of an olive gray, the sides and 
operc.ula are silvery, the former, however, according to 
Edward, with different shades of colour between the 
several longitudinal ridges. The space between the two 
ridges nearest to the back is of a deep amber, the 
next strip greenish blue, the third space, just below 
the lateral line, silvery white with a bright metallic 
lustre; the lower spaces are similar to the upper, but 
their colours are fainter. The belly is then grayish white, 
with a dash of greenish blue and purple. The fins are 
for the most part transparent, the dorsal pale gray, the 
anal white, the caudal of a deeper gray, with “a dark 
longitudinal mark along either lobe near to its outer 
edge” (Day). The paired fins are pale, “of a faint rose 
colour” (Moreau). “A black spot on the upper edge 
of the orbit, and a smaller one on the snout” (Day). 
“ According to Moreau the ordinary length of this species in the Mediterranean Sea is 14 — 20 cm. Collett’s largest specimen 
from Norway was 265 mm. long. 
1 Collett states as a change of growth that, in young specimens (with the length of the body to the end of the caudal lobes less 
than 15 cm.), the greatest depth is about '/ g , in the oldest specimens (more than 21 cm. long) about 1 ,/ 6 , of the said length of the bodj 7 . 
