300 BRITISH FRESH-WATER FISHES 
as in the sturgeon. It is armed with horny teeth, which, in 
spite of the circular form and boneless character of the orifice, 
can be distinguished as maxillary, mandibulary, lingual, and 
suctorial. The eyes, which are only rudimentary in the larval 
stage of the animal, are developed in maturity, but they are 
very small. They are placed one on each side of the head, 
close in front of the seven gill-openings, with which they have 
the appearance of forming one series, The single nostril is 
in the middle of the upper side of the head, and ends in a 
blind sac, without perforating the palate. 
The Lamprey (Petromyzon marinus) 
The name “lamprey ” comes to us through the Old French 
lamproie, a contracted form of the Low Latin /ampreda, which 
is a transposition of the older form J/ampetra, the licker of 
rocks or stone-sucker. The peculiar habit of the fish in 
adhering by its mouth to stones, and even lifting them, is 
the obvious source of the name, and the Greek equivalent, 
Petromyzon, has been assigned as the scientific title of the 
genus. 
The length of the lamprey is about fifteen times greater 
than its utmost depth. The skin is very slimy, and usually 
coloured grey or yellowish-grey on the back and sides, 
abundantly spotted or marbled with dark brown or black. 
There are two dorsal fins, whereof the second is confluent 
with the caudal fin. The eyes are very small, situated just 
in front of the seven circular gill-openings. The single nostril 
is on the top of the head, between the eyes, and is encircled 
by white spots. The most remarkable feature is the mouth, 
which, when open, forms a disc, without any indication of 
division into jaws, round which the teeth are arranged in rows, 
large in front and small behind. In the middle of the disc, 
at the back of the throat, is a plate armed with seven or eight 
strong teeth, and the tongue also carries three teeth. Outside 
