COTTOIDS. 
157 
is overgrown with seaweed; but some peculiar forms 
make their way to the abysses of the ocean, while 
others have become fresh-water fishes, the former {Cot- 
tunculus) presenting a certain likeness to IAparis and 
the latter (the subgenus Uranidea ) to Gobius. 
Jordan and Gilbert estimate the number of spe- 
cies within this subfamily at about 150, distributed 
among about 40 genera and subgenera. Those genera 
which belong to the Scandinavian fauna, may be di- 
stinguished as follows: 
A : One continuous dorsal fin Genus Cottunculus. 
B: Two distinct dorsal fins: 
1: Less than 20 rays in the anal fin: 
a: Palatine bones toothless: 
act: Vomer toothless: Genus Gymnocanthus. 
hb: ,, with teeth: ,, Cottus. 
b: Palatine bones with teeth :_ ,, (Jentridermiclithys. 
2: More than 20 rays in the anal fin : ,, Triglops. 
Genus COTTUNCULUS. 
rays, wrapped in a loose skin, form the anterior , lower part of the continuous dorsal fin. 
hut granulated, or rough with small spines. Read large. The four preopercular spines 
Fine, car diform teeth on the lower jaw, the intermaxillary hones and the vomer, 
to the broad isthmus, which is without any transverse fold. No gill-slit behind 
the fourth , branchial arch. 
Weak, , flexible spinous 
Skin without true scales, 
obtuse, and covered with, skin. 
Branchiostegal membranes united 
We assign the first place among the Scandinavian 
Cottoids to this genus, which is without doubt the most 
marked metamorphosis of the Cottoid type among the 
forms of which we have to treat. It was first remarked 
and characterized as a distinct genus by Collett in 
1874. Its metamorphosis is connected, however, in 
several respects with a retention of the juvenile cha- 
racters of the type. It is one of these characters that 
most distinctly marks the genus, namely, the confluence 
of the two dorsal fins, or, more strictly, their retention 
of this condition. They are united in the same way, 
and with almost the same relations to each other in 
respect of size, or at least of height, in the most de- 
veloped young specimen of Cottus scorpius (fig. 44) 
which Agassiz has figured". 
Another juvenile character may be found, as Col- 
lett has remarked, in the coloration of the Scandi- 
navian species, with its sharply defined, black, trans- 
verse bands on the head, body and fins. The close 
proximity of this genus to Cottus in other respects is 
best shown by the typical (quadrangular) arrangement 
of the parietal spines, the anterior pair of which are, 
Fig. 44. A young specimen of Cottus scorpius, 1 1 l / 2 nun. in length. 
Magnified. After A. Agassiz. 
however, situated on the forehead in a line with the 
hind margin of the eye. 
Three, perhaps four, species of this genus 6 are 
known to exist in the dee}) water in the north of the 
Atlantic. Only one of these species belongs to the 
Scanclin avian fan na. 
a Proc. Amer. Acad. Arts. Sc., vol. XVII, Young Osseous Fishes, pi. II, fig. 2. The same changes of development in the mutual 
relations of the two dorsal fins are shown in the result of Sundevall’s observations of the development of Cottus gobio (Vet. Akad. Handl., 
vol. I 1855), Om fishy ng els utveckling , p. 7, pi. I, figs. 8 and 4. 
h Cottus thorns onii Gthk, Proc. Roy. Soc. Edinb. vol. XI (1881 — 82) p. 079. Cottunculus towns, Goode, Proc. U. S. Nat. Mus. 
1880, p. 479; Jord., Gild., Bull. U. S. Nat. Mus., No. 1G, p. G88. 
