MINNOW. 
755 
or 99 mm. to the tips of the middle caudal rays. From 
Ireland, however, though the species is supposed to 
have been planted there, Thompson mentions a speci- 
men 6 in. (152 mm.) in length. The females attain 
a greater size than the males. In shoals of spawning 
Minnows Heckel and Kner found the length of the 
females to vary between 92 and 105 mm., that of the 
males between 52 and 79 (exceptionally 92) mm. The 
largest specimens in their possession were 131 mm. 
long and came from Hungary. 
The body is elongated and of fairly uniform thick- 
ness, the anterior part of the trunk showing so little 
compression that the greatest thickness is at least a j 3 
of the depth. Posteriorly the lines of the body con- 
verge, as usual, even from the sides, but the tail is 
still comparatively terete. The depth of the head at 
the occiput is slightly greater than its breadth. The 
back is broad and depressed in the median line into 
a groove, which may be exchanged in front of the 
dorsal tin for a low carina. The belly is even and 
terete, or, at the isthmus, flat. The dorsal profile shows 
a more or less distinct break at the occiput, but is 
otherwise regular, like the ventral profile, which differs 
from that of the other Whitefishes in being free from 
any perceptible break, even at the vent or along the 
anal fin. 
The most characteristic point in the form of the 
head consists of a swelling (thickening of the ethmoid 
bone) on the snout between the nostrils. The occiput 
and forehead are slightly convex or (especially the 
latter) nearly flat; the gill-covers and cheeks almost 
perpendicular. The eyes are middle-sized and set so 
high that their superior margin lies almost in the same 
plane as the forehead. Their longitudinal diameter 
measures in young specimens ( x / 2 dm. long) about 30 
%, in average- sized specimens about 28 %>, and in spe- 
cimens 1 dm. long about 23 %, of the length of the 
head; the vertical diameter is 9 /io — Vs °f the longi- 
tudinal. They lie almost entirely in the anterior half 
of the head, the postorbital length of the latter being- 
only slightly less than the length of the snout and the 
eye together. The breadth of the interorbital space is 
always greater than the diameter of the eyes and va- 
ries between 40 and 30 % of the length of the head. 
The horizontal profile of the snout is obtusely (slightly) 
rounded, and its tip generally projects a little beyond 
that of the lower jaw. The cleft of the mouth, with 
its fleshy lips, is small and turned slightly upwards. 
The length of the upper jaw from the middle of the 
tip of the snout is, as a rule, equal to that of the 
snout, or about 30 % of that of the head. The length 
of the lower jaw is about the same as the breadth of 
the interorbital space, or on an average 1 /. i of the length 
of the head. The nostrils are round and rather large, 
but set close together, the posterior nostril being usu- 
ally covered to a great extent by the dermal flap that 
rises from the narrow bridge between them. They lie 
much nearer to the eyes than to the tip of the snout. 
The gill-openings are comparatively large, extending 
above along about half the upper margin of the gill- 
cover, and separated at the isthmus by a distance some- 
times scarcely half the diameter of the eyes. The 
branchiostegal rays as well as the rim outside them are 
broad. The gill-rakers are small; in the outer row on 
the first branchial arch they are about 8 in number, 
scattered, verrucose, and hardly distinguishable. The 
pharyngeal teeth show considerable variation in number. 
In most cases they are set in two rows, the large row 
on the inside of the lower arm of the bones generally 
containing 5 teeth on the left side and 4 on the rig-ht, 
and the smaller row, outside the former one, consist- 
ing of 2 small, almost cylindrical teeth. Sometimes, 
however, not a trace of this smaller row can be found. 
We have never found the pharyngeal cartilage present: 
according to Fatio it is of an obtuse heart-shape, with 
the posterior part attached like a knob to the anterior. 
Our figure (fig. 188, c) shows, on the other hand, 
how the mucous membrane of the pharynx covers the 
downward process of the occipital bone at the spot 
where the pharyngeal cartilage is otherwise developed. 
This figure may also assist in the explanation of the 
form possessed by the pharyngeal cartilage in the ma- 
jority of the following Leuciscines, at least in the larger 
ones. The surface of this cartilage is heart-shaped. 
On each side of it the roof of the pharynx shows deep 
hollows, converging in a forward and upward direction 
(downward in the figure, which is drawn from a spe- 
cimen laid on its back, with the head turned towards 
the artist). But at the middle of the base of this 
heart-shape the mucous membrane is continued (up- 
ward in the figure) in a rounded (convex) coat over 
the lower (posterior) part of the said occipital process, 
until it leaves this process and passes into the upper 
wall of the oesophagus. This convex part forms the 
foundation of the callosity which, especially in the 
larger Whitefishes (see, for example, the Chub, fig. 
