270 
SCANDINAVIAN FISHES. 
Nat., tom. IX (1874), p. 310; Coll. ( Latrunculodes ), Forh. 
Vid. Selsk. Christ. 1 874, p. 151; ibid., Tilkegsh., p. 60; 
Id. (Crystallogo bins'), ibid. 1876, No. 6, p. 26, tab. II, fig. j 
9 — 14; Malm, Gigs, Boh. Fn., p. 651; Coll., 1. c. 1879, 
No. 1, p. 36; Day, Fish. G:t Brit., Irel,, vol. I, p. 172, 
tab. LIII, fig. 4; Lillj., Sv., Norg. Fisk., vol. I, p. 640; 
Coll., N. Mag. Naturv., Christ,, Bd. 29 (1884), p. 63. 
Crystallogobius Nilssonii, is essentially of the same 
form as the preceding species, and of equal or even 
greater transparency. The body is, however, still more 
strongly compressed; and the great length of the second 
dorsal and the anal fins, the shortness of the first dorsal 
fin, and the arcuate, upturned form of the lower jaw, 
with the peculiar structure of the teeth in the male 
(fig. 72, d and e), combine to give this species an en- 
tirely different appearance. Another remarkable point 
in this fish is the broad (inultiradiate), somewhat lobate 
form of the pectoral fins, with their semicircular, mus- 
cular root and elongated, roundish shape, furnished as 
they are with short, fine rays at the top and bottom, 
and with the middle 12 — 14 rays longest, though much 
shorter than in the preceding species, and even in the 
males only about 10 % of the length of the body." When 
expanded, the pectoral fins are as deep as the body. The 
development of the fins in this species is, however, 
widely different in the different sexes. The second ray 
in the first dorsal fin is the longer, and the fin-mem- 
brane sometimes extends back to the beginning of the 
second dorsal fin, but is generally much shorter. In 
the females (fig. 72, c) this fin is remarkably low, 
being often scarcely distinguishable, which is also the 
case with the ventral fins, while the second dorsal and 
anal fins are also lower in the female than in the 
male, and the pectoral fins much shorter. According 
to v. Duben and Koren’s measurements of specimens 
from 31 to 42 mm. long, the fins also undergo con- 
siderable changes of growth, the base of the second 
dorsal fin increasing from 30 to 35 % of the length of 
the body, the base of the anal fin, on the other hand, 
being reduced from 36 to 35 % thereof, while the dis- 
tance between the tip of the lower jaw and the vent 
is reduced from 45 to 42 % of the length of the body, 
and the distance between the first dorsal fin and the 
tip of the snout from 23 to 22 %. According to the 
same measurements the greatest depth of the body 
sinks from 13 to 11 % of the length, and the least 
depth from 8 to 7 1 Again, according to the same 
measurements, the length of the head is about 17 % 
of that of the body; but in two females, 3.3 and 38 
mm. long, sent us from Christiania Fjord, by Pro- 
fessor Collett, this ratio varies between 15 and 16 %, 
and in two males from the same place, 44 and 45 mm. 
long, it is 20 %. The longitudinal diameter of the 
eye decreases, according to v. Duben and Koren, from 
29 to 23 V 2 % of the length of the head. In our own 
specimens the length of the lower jaw varies between 
5 6 7 2 and 60 % of that of the head. 
To the best of our knowledge Crystallogobius Nils- 
sonii has only twice been found in Sweden, on both 
occasions near the entrance of Gullmar Fjord. In July, 
1877, off Gaso, Malm found a male and a female which 
had probably been drawn up in a net from a depth of 
14 fathoms; and among the collections which Dr. Wi- 
ren brought with him in 1885 from the Zoological 
Station of Christineberg, was a male specimen 36 mm. 
in length. On the Norwegian coast, on the other hand, 
it has repeatedly been met with, in some years in 
fairly large numbers, though at other times, like the 
preceding species, it seems to be extremely rare. The 
first specimens, 5 in number, were taken by Stuvitz 
off Steen, near Bergen, in December, 1834. Off Aske- 
wold, in the north of the Department of Bergen, Go- 
vernor Christie took two specimens, which were 
also placed at v. Duben and Koren’s disposal in the 
Museum of Bergen. These writers also mention two 
other specimens which they had personally taken in a 
dredge, at a depth of about 30 fathoms, off Christi- 
anssund, in July. 1843. Each of these specimens was 
found hidden in the empty shell of a worm ( dice - 
topterus norvegicus ). Both of the Norwegian zoologists 
Sars have subsequently met with this species at several 
spots in the south of Norway; and in recent years, 
from 1875 to the present time, it has repeatedly been 
found by Collett during the seine-fishery for Macke- 
rel, Sprats and Cod in Christiania Fjord. In June, 
1879, in particular, he took about a hundred specimens 
among a small shoal of Herrings that was netted in 
Sandvig, some Swedish miles south-west of Christiania. 
June is approximately the spawning-season of this 
species; and its habits are in all probability much like 
those of Aphya minuta, in company with which it is 
often found. Like the latter species it is also com- 
prised among the fishes called A at by the Norwegians, 
Id this respect Collett’s figure is less accurate than v. Duben and Koren’s and Day’s figures above referred to. 
