Il. COTTOIDS OF NORTH AMERICA. 33 
CHAP THER IVP. 
ON THE GENUS COTTUS, Artedi. 
§ 1. ZootocicaAL CHARACTERS. 
Resrricrep within the limits which we have assigned to it,! the genus Cottus 
still comprehends a considerable number of species which, although apparently cast 
in the same mould, are nevertheless distinct, as will, we hope, appear from their 
descriptions and figures. 
The characters of the genus consist in the presence on the preopercular of one 
spine only, which is situated at the posterior angle of that bone, and is curved 
upwards and backwards. Sometimes a much smaller spine is to be found beneath, 
and in one instance there is a third one of the same size as the second, directed 
downwards. ‘The inferior edge of the subopercular is also provided with a similar 
minute spine, having its point directed forwards, and generally completely concealed 
under the skin and muscles. The head consequently has a smooth appearance 
which contrasts singularly with the spiny head of Acanthocotti, or marine Cotti 
of authors. The mouth is but little cleft, and its angles seldom extend beyond 
the anterior rim of the orbit. The lips which line the jaws are capable of more 
or less expansion along the branches of the jaws, and at the angle of the mouth. 
The premaxillaries, the dentaries and the vomer, are the only bones provided with 
truly characterized, although very small, card-like teeth. In their immature state 
some species exhibit teeth-like asperities on the palatines. This occurs chiefly 
amongst those having four jointed rays to the ventrals: in C. Wilsonti, C. Bairdii, 
and C. meridionalis, C. gracilis is the only one of the division with three jointed 
rays, where similar asperities have been noticed. This character of palatine teeth, 
which is merely shadowed in the genus Cottus, acquires a full development in other 
genera, thus constituting a permanent feature and assuming an actual signification. 
The eyes are situated near the summit of the head, more or less approximated 
on the frontal line. There are constantly two nasal openings; a tubular one, 
placed along the space comprised between the anterior border of the eye and the 
extremity of the snout; the other is even with the surface of the skin and situated 
backwards, behind and above the former and very close to the orbit. The latter 
opening has been but recently discovered, having generally been overlooked on 
1 Proc. Bost. Soc. Nat. History, iii. 1851, p. 183. 
