SCOPELOIDS. 
923 
eyes and optic nerves are entirely aborted, the fish 
being consequently quite blind". But under the ex- 
tremely thin and transparent roof of the skull (an- 
swering to the parietal and frontal bones, which are 
hardly distinguishable), and forward over the wide pa- 
latine arch, thus extending above nearly the whole 
surface of the flattened head to the posterior limit of 
the nasal region, there lie a pair of lamelliform lumi- 
nous spots, separated from one another by a longi- 
tudinal median septum rising from the roof of the 
mouth. Above each of these luminous spots run both 
the frontorostral branch of the cephalic system of the 
lateral line and the nasal branch of the fifth pair of 
cranial nerves. The position of these luminous spots 
is thus, like that of the parietal organ, intracranial. 
With regard to their function Gunther remarks: “The 
power of producing light, and thereby attracting other 
creatures, must be of great use to a fish, which, de- 
prived of organs of sight and touch, would be unable 
to procure its food.” 
As we have mentioned above (p. 826, note/), Gun- 
ther'' has proposed to range the Scandinavian members 
of this family in two families, the Stern op tychidce and 
Scopelidce. But the difference between these two fa- 
milies is hardly appreciable. They occupy an inter- 
mediate position between the Salmonoid and Clnpeoid 
families. In common with the former they possess an 
adipose fin behind the true dorsal fin, and their ovaries? 
like those of the latter, are furnished with a special 
oviduct. The adipose fin is often very small, but in 
most cases furnished with fibrillous (cartilaginous) rays. 
The distinction adopted by Gunther consists merely 
in the greater or less length of the intermaxillaries, 
the posterior part of the margin of the upper jaw being 
formed in his S ter nop tychidce by the maxillary bones. 
But these bones often coalesce so closely with the in- 
termaxillaries that the limits between them can hardly 
be detected. The utility of the character is thus con- 
siderably reduced. On the other hand it happens, in 
Gunther’s Scopelidce , that the hind part of each inter- 
maxillary bone is firmly applied to the outer surface 
of the maxillary, above the lower margin of the latter. 
Consequently the said margin may form part of the 
margin of the upper jaw in this family as well, though 
in such instances it is toothless. We therefore prefer 
the older opinion, embraced in recent times by Moreau*' 
and retain the Scopeloid family in its entirety. It 
then contains about eighty species of marine fishes, 
most of them deep-sea forms or nocturnal surface-fishes 
but some belonging to the littoral regions of the tropic 
seas. The Scopeloids belonging to the Scandinavian 
fauna may be distinguished as follows: 
1 : Snout shorter than the postorbital 
part of the head. Dorsal fin situated 
about half-way along the body. 
A: Abdominal part of the body ex- 
ceedingly deep and compressed ; 
its ventral margin sharp and se- 
parated by an abrupt break from 
the under surface of the tail. 
(Subfamily S ter nop ty chince) Argyropelecus Olfersii. 
B: Abdominal part of the body pass- 
ing uniformly (without sharp 
break) into the caudal part, and 
with more or less terete ventral 
margin. 
a: Maxillaries furnished with 
teeth behind, and entering 
into the structure of the mar- 
gin of the upper jaw. (Sub- 
family Cocciinui). Preabdomi- 
nal length greater than the 
postabdominal. _ Maurolicus Mulleri. 
b: Maxillaries toothless, and as 
a rule forming no part of the 
margin of the upper jaw (Sub- 
family Saurince). Preabdomi- 
nal length less than the post- 
abdominal. 
a: Length of the base of the 
dorsal fin more than ] / 5 of 
that of the body. Longi- 
tudinal diameter of the eyes 
less than 1 / 2 of the post- 
orbital length of the head. Myctophurn elongatum. 
(3: Length of the base of the 
dorsal fin less than l / 6 of 
that of the body. Longi- 
tudinal diameter oftheeyes 
more than ‘/ 2 of the post- 
orbital length of the head. Myctophurn glaciate. 
2: Snout longer than the postorbital part 
of the head. Dorsal fin situated far 
back (Subfamily Paralepidince). No 
luminous spots Sudis atlanticus. 
“ Also without olfactory nerves, according to Moseley. 
b Cat. Brit. Mus., Fish., vol. V, pp. 384 and 393. 
c Hist. Nat. Poiss. Fr., tome III, p. 491. 
