744 
SCANDINAVIAN FISHES. 
— and which in its most advanced development has 
given rise to the establishment of a distinct species, 
Gobio obtusirostris. This swelling — even when it is 
not very prominent — and also the projection beyond 
the mouth of the blunt tip of the snout most strongly 
characterize the head of the Gudgeon. The length of 
the head varies between about 1 / i and a little more 
than * 1 / 5 (26 — 22 %) of that of the body, being as usual 
comparatively greater during youth. The eyes are ex- 
tremely mobile, round, set fairly high — their upper 
margin being almost in a plane with the slightly con- 
vex forehead — and rather large, their longitudinal 
diameter varying between about 7 and 47 8 % of the 
length of the body or about 27 and 21 % of the length 
of the head. In young specimens this longitudinal dia- 
meter is about equal to the breadth of the interorbital 
space, in old less, sometimes only 7 /io thereof. The posi- 
tion of the eyes is also such that the length of the snout 
— with considerable individual variations" — measures 
on an average 2 / 5 of that of the head. The nostrils lie 
on the rounded margin between the sides and back of 
the snout, much nearer to the eyes than to the tip of the 
snout. Together they form on each side a round cavity, 
divided externally by the oblique partition Avail betAveen 
them, which is raised into a lid. The mouth is small 
and lies, as Ave have mentioned, entirely on the under 
side of the head, with the maxillary bones extending 
back to about a line Avith the anterior nostrils and 
Avith the articulation of the loAver jaAv in a line Avith 
the anterior margin of the orbit. The lips are fleshy, 
and the dermal fold that, lies on each maxillary bone 
is elongated behind into a barbel of moderate length, 
Avhich extends when laid back hardly any distance, if 
at all, behind the perpendicular from the anterior mar- 
gin of the eye 6 . The palatal curtain Avithin the upper 
jaw is well-developed. The tongue is fleshy, but hardly 
at all free from the bottom of the mouth. The gill- 
rakers are short, scattered, blunt, and soft, developed 
on the first branchial arch only in the inner (posterior) 
row, which contains about 8. Among the pharyngeal 
teeth (fig. 186) only the three posterior in the inner 
roAv have a distinct, obliquely cut masticatory surface, 
Avhile the others — both the two anterior, thicker teeth 
in the inner row and the tAvo or three teeth in the 
outer i*oav — are of a straighter cylindrical form, though 
obliquely hooked at the tip. The pharyngeal cartilage 
is soft, scarcely cartilaginous, and triangular, with the 
upper (anterior) side slightly curved upAvards (convex). 
The pseudobranchim are distinct on the inside of the 
upper part of the hyomandibular bone, though small, 
with about 6 filamentous lamellae. The operculum is 
trapezoidal, its upper and loAver sides being parallel, 
but the former only about 2 / 3 as long as the latter and 
throughout united to the dorsal side. The branchiostegal 
membrane is extraordinarily narroAV along the hind 
margin of the operculum, but all the broader along the 
suboperculum and in its loAver part, where it is ex- 
tended by three, fairly broad, sabre-shaped rays. The 
height of the gill-openings is about equal to the post- 
orbital length of the head; their upper angle lies hardly 
on a level Avith the superior margin of the eye, and 
their loAver angle lies in about a line Avith the hind 
margin of the preoperculum, Avhere the branchiostegal 
membranes on the ventral side coalesce Avith the 
isthmus. 
The dorsal fin is trapezoidal, Avith the upper mar- 
gin straight or slightly concave and the high anterior 
margin composed of the first three (simple) rays. The 
first of these rays is extremely short, sometimes scar- 
cely possible of external detection, Avhile the second is 
nearly half as long as the third. The fin begins at a 
distance from the tip of the snout,' Avhich measures on 
an average 42 % (varying between 41 and 43 %) of 
the length of the body, and its length (base) is 11 or 
12 % (in the males sometimes nearly 13 %) of the 
same. Its height (the length of the third ray) is always 
greater than its length and varies between about 16 
and 21 % of the length of the body. 
The anal fin is of the same form and structure as 
the dorsal. Its distance from the tip of the snout is 
on an average 62 % (varying betAveen 60 and 63 %), 
its length l l / 2 % (varying betAveen 7 and 8 7 2 %), and 
its height 137 2 % (varying betAveen 12 and 16 %) of 
the length of the body. 
The caudal fin is deeply forked at the hind mar- 
gin, most so in old specimens, and thus forms an ob- 
tuse angle Avith soineAvhat convex edges to the lobes. 
The length of the middle rays, Avhich occupy about 
11 — 9 % of the length of the body, is as a rule in 
young specimens equal to or a little more than half, 
° Varying between 34 and 45 / of the length of the head. 
6 Canestrini, however, mentions a specimen, a male 74 1 / 0 mm. long, in which the length of the barbels was somewhat more than 
