810 
SCANDINAVIAN FISHES. 
imbricated, and a. greater part of their surface is thus 
left bare, the rule being that in this hybrid most of 
the scales, at least those on the middle of the sides of 
the body, have the free (hind), externally visible por- 
tion half (or more) as long as deep, while in the pre- 
ceding hybrid, as in the Rudd and the White Bream, 
the length of the said part of each scale is less than 
half its depth. The same difference in the position 
of the dorsal tin as appears between the Roach on one 
hand, the Rudd and White Bream on the other, is 
also maintained here, the distance between the tip of 
the snout and the beginning of the said tin being less 
in this hybrid than half the length of the body. In 
the specimen examined, it is true, the dorsal tin con- 
tains 9 branched rays; but the last of them is slender 
and branched only at the tip, not, as is generally the 
case in the Cyprinoids, divided almost to the base. 
The pharyngeal teeth we have not been able to exa- 
mine; the above remark on this head is taken from 
Jackel, who found them to number: 0(1 or 2), 6(5) 
— 5(6), 0(1 or 2). 
This form, according to Mr. Svensson, is the most 
common hybrid in the River Helge and the lakes 
through which this river flows as it approaches the 
sea. Kristianstad Museum possesses three stuffed spe- 
cimens, one of which ive have been enabled to examine 
by the kindness of Lecturer Wahlstedt. It is a male, 
caught on the 4th of May, 1872, with the small, ver- 
rucose tubercles characteristic of the spawning season, 
on the sides of the head (thickest on the gill-covers), 
the lateral scales on the forepart of the body, and the 
inner surface of the pectoral tins. The coloration seems 
to have been that typical of the Roach, the front part 
of the anal fin, however, being of the black colour 
frequently present in the White Bream. The entire 
length to the tip of the lower caudal lobe is 29 cm., 
but to the end of the middle caudal rays — the measure- 
ment constantly termed in this work, unless other- 
wise specified, the length of the body — only 256 mm. 
The greatest depth is 30'7 %, and the least depth 10 %, 
of the length of the body. The greatest thickness — 
in the stuffed specimen just in front of the dorsal tin 
— measures 37*6 % of the greatest depth. The length 
of the head is 20'7 % of that of the body, and the 
postorbital length of the same part half the entire 
length of the same. The distance from the tip of the 
snout to the beginning of the dorsal tin is slightly less 
than half the length of the body. The base of the 
dorsal tin measures 12*5 %, its longest ray 20'3 %>, of 
the length of the body, ahd its last ray rather more 
than 1 / 3 (347 2 %) of the length of the longest ray. 
The beginning of the anal tin lies at a distance from 
the tip of the snout equal to 65*6 % of the length of 
the body; its base measures 16*8 %, its longest ray 
15 %, of the same length. The length of the pectoral 
fins is 16 % of that of the body. The ventral fins 
are only slightly shorter than the pectoral, and the 
distance between them and the tip of the snout is 93 
% of that between the dorsal tin and the same point. 
The length of the middle caudal rays occupies 9 % of 
that of the body. Apart from all the other resem- 
blances to the Roach, the position of the ventral tins 
in relation to the beginning of the dorsal tin shows 
that one of the parent species of this hybrid must have 
been the Roach; while the length of the pectoral tins 
and the number of the scales admit of the assumption 
that the White Bream was the other parent species, 
but exclude the Bream from the possible progenitors 
of this hybrid. 
From the same localitv the Museum of Kristian- 
stad has received two other hybrids, similar to each 
other, one of which is mentioned by Qvennerstedt 
(1. c.) under the head of “Ex. 2”. The other (tig. 202) 
was caught on the 17th of March, 1869, and has been 
lent to me for the purpose of examination by Mr. Wahl- 
stedt. It has the coloration of the White Bream, in 
particular the above-mentioned black spots' 1 on the 
sides of the body, the dorsal, anal, and caudal fins, and 
the right ventral tin. Two similar spots of somewhat 
larger size, with the same symptoms of skin-disease, 
are situated on the right side of the head, the lower 
on the hind margin of the preoperculum, the upper 
on the front margin of the operculum. The specimen 
evidently has more White Bream blood in it, a cir- 
a These spots, which are reproduced in our figure, cannot be minutely examined in a dried specimen, but are probably caused by 
Holostomum cuticola (Nordmann, Mikrographische Beitrcige zur Naturgeschichte der icirbellosen Thieve, Heft. I, p. 49, taf. IV, fig. 1 — 4), a 
flatworm occurring in the skin and eyes of many fishes, and belonging to the Trematod order — cf. for example fig. 211, p. 209 in Max 
von dem Borne, Handbuch der Fisrhzucht und Fisclierei. The spots themselves are pure black; and the scales over which they extend are 
partially abraded. At the centre of some spots is a blister, concealing a cavity which was probably inhabited by the parasitic worm. 
