ARGYROPELECUS OLFERSII. 
929 
their surface show any regular streaks or the like.” 
Of the lateral line v. Duben and Koren saw only a 
trace, “in the form of an elevated line beginning be- 
low the origin of the true dorsal tin, and running 
along the middle of the body to the base of the 
caudal tin.” 
The luminous spots are distributed as follows. 
On the under side of the lower jaw — on the soft 
chin" — below the tip of the lingual bone, lie two ra- 
ther undefined spots, which are probably luminous 6 , 
though in this species, to the best of our knowledge, 
they have not yet been examined. On the ceratohyoid 
bones, in the skin between the bases of the first (low- 
est) 7 branchiostegal rays, there are 6 small luminous 
spots on each side of the body. Behind these each 
side of the isthmus is furnished with 6 larger luminous 
spots, gradually increasing in size as the isthmus grows 
deeper behind. These are succeeded, on each side of 
the sharp preabdominal margin of the belly, by a row 
containing 12 luminous spots of fairly uniform size, 
somewhat smaller than those on the isthmus and small- 
est at the ' beginning and end of the row. Above the 
rows on the isthmus and the preabdominal margin each 
side of the body bears a row of 10 luminous spots; 
but this row is interrupted and belongs partly to the 
head, partly to the abdominal region. One spot lies 
within the anterior (horizontal) arm of the preoper- 
culum, but spreads downwards over the anterior part 
of the interoperculum. Another, smaller spot occupies 
the lower part of the suboperculum and the hind part 
of the interoperculum. Two large spots adjoin to the 
hind margin of the clavicle above the insertion of the 
pectoral fin, and are indeed vertical in direction, but 
set so that their tops form a continuation of the curve 
followed by the upper parts of the spots on the isth- 
mus. The remaining six abdominal spots are about 
equal in breadth to the last-mentioned pair but shorter 
than they, and lie in a continuous, horizontal row, but 
lower than the last-mentioned pair. Each of them 
occupies the space between two ribs, and lies vertically 
or obliquely above one of the spots in the lower pre- 
abdominal row, the penultimate spot, however, being 
situated above the penultimate two in the lower row, 
both of which occupy the same intercostal space. The 
segmental arrangement of the luminous spots is thus 
not observed with complete uniformity. Each side of 
the postabdominal margin bears a continuous row of 
4 luminous spots. Owing to the singular form of the 
body these spots are indeed set at the ventral margin, 
i. e. their lower parts extend thither, but also on a 
level with the two large spots above the insertion of 
the pectoral fin. In size they answer most nearly to 
the spots in the upper preabdominal row, which they 
also resemble in the circumstance that the spots on 
one side of the body do not coalesce internally (supe- 
riorly) with those on the other side, as is the case 
with the lower preabdominal row. The postabdominal 
spots on one side of the body are also separated in- 
teriorly from those on the other: their defining walls 
do not coalesce below, like those of the preabdominal 
spots, into a median edge. On each side of the body 
the walls coalesce into a more or less high, thin rim, 
and together form in this manner a groove or deep 
channel, open below, at the hind extremity of which the 
vent is situated. The luminous spots on the tail form 
two groups, the one, along the posterior two-thirds of 
the base of the anal fin, being a row of 6 rather large 
spots, the 2nd, 3rd, and 4th smaller than the rest, the 
other a row of 4 smaller spots at the inferior margin 
of the tail, just in front of the caudal fin. All these 
luminous spots thus belong to the lower part of the 
body. Higher up we find, however, an isolated lumi- 
nous spot on each side of the head, on a level with 
the tip of the snout. This spot is situated on the 
uppermost part of the preoperculum, just below its 
articulation. 
The above description of the luminous spots in 
Argyropelecus Olfersii applies in every detail to the 
analogous organs in Argyropelecus hemigymnus , a Me- 
diterranean and Central Atlantic form which in other 
respects too so closely I’esembles A. Olfersii that it 
evidently represents a lower stage in the same course 
of development. 
Argyropelecus Olfersii has been named after a 
Prussian diplomatist who, while on a voyage to Brazil, 
secured an example of this species that had become 
entangled among weeds to a lead-line, “between the 
Canary Islands and Brazil.” The specimen figured by 
Cuvier (1. c.) was found by Dussumier some kilom. 
south-east of the Cape of Good Hope, among a floating 
a Mention, pars inter gnathidia mollis (Sundevall). 
b Cf. Argyropelecus hemigymnus and Sternoptyx diaphana, Lendenfeld in Gunther, Deep Sea Fish., 1. c., p. 314. 
