334 
PISCES. 
appearance of sacs produced by the union of the faces of the proximate ones. The labyrinth of the ear 
is embedded in the cranium, and the nostrils opened by a single orifice, in front of which is a blind , 
cavity, improperly thought a spiracle. The intestine is straight and slender, with a spiral valve. 
Petromyzon, the Lampreys, have seven gill-openings on each side, and the skin on the upper and under parts of 
the tail is formed into fin-like crests, which, however, have no rays. The Lampreys properly so called, have strong i 
teeth in the maxillary ring, and the inner disc of the lip, which is very circular, is covered with tubercles, hard and !| 
crusted like teeth : this ring is suspended by a transverse plate answering to the intermaxillaries, and there are f 
vestiges of maxillaries on the sides. The tongue, which moves backwards and forwards like a piston, and performs 
the suction, has two longitudinal rows of small teeth. Water reaches the gills; from the mouth by a particular •; 
membranous canal, a sort of trachea, placed under the gullet and perforated with holes ; there is a dorsal before i 
the vent, and another behind it which unites with the caudal. They habitually fix themselves to stones and other 
hard substances by means of the sucker ; and they attach themselves to the largest fishes in the same manner, and 
in the end pierce their integuments and prey upon their substance. 
The species are— P. marinus, the Sea Lamprey, two or three feet long, marbled with brown and a yellow ground; 
the first dorsal separate from the second ; two large teeth on the upper part of the maxillary range. In spring they ; 
approach the mouth of rivers, and their flesh is highly esteemed. P. fluviabilis, the River Lamprey, from a foot to 1 
eighteen inches long ; silvery, with blackish or olive spots on the back ; two large teeth in the maxillary ring; found j 
in the fresh waters. P. planerii, the Small River Lamprey, is eight or ten inches long, and has the colours and j 
teeth of the preceding : it also inhabits the fresh waters. [The last two are often styled Lamperns.] I 
Myxine. — The members of this genus have but one tooth in the maxillary ring, which is entirely membranous ; ,i 
two rows of strong teeth on each side of the tongue ; but in other respects like the Lampreys. The mouth is i 
circular, with eight cirri, and has a spiracle on the upper margin which reaches the interior. The body is cylin- j 
drical, and furnished with one fin round the extremity of the tail. The intestine is straight, but simple, and plaited 
internally, and the liver has two lobes : no eyes are perceptible. Their eggs grow to a large size ; they discharge ij, 
so much mucus from the pores in their lateral line that if kept in a vessel of water they turn it into a jelly ; they j: 
attack fishes in the same manner as the Lampreys, and they are divided into subgenera according to the number | 
of their gill-openings. i 
Heptratremus, has seven on each side, like the Lampreys, and the only known species is from the South Sea. 
Gastrobanclius, has a common canal to the gills on each side, each of which opens by a hole near the heart, and i! 
at one third of the length from the head. G. glutinosa, the Hag, is the only known species, and it enters the mouths j< 
of fishes when on the fishermen’s line, and plunders their substance. j I 
Ammocetes, has the entire skeleton so soft and membranous that there is not a bone in the whole, not even a | 
tooth ; they have the external form and gill-openings of the Lampreys, but their fleshy lip forms only a semicircle l| 
on the upper part of the mouth, which is furnished with numerous cirri. The known species, A. brancMalis, is |! 
from six to eight inches long, about the thickness of a goose-quill, and of no use but as bait for other fish. [It has fij 
been accused of sucking the gills of other fishes, but perhaps falsely. It is found in the sand and mud of small j j 
streams ; preys on worms, insects, and dead matter, and is, in return, preyed on by the Eel.] | 
[^Amphioxus, has the body compressed, the surface without scales, and both ends pointed. It has a dorsal along : i 
the whole line of the back, but no other fins. The mouth is on the under side of the body, opens longitudi- i il 
nally, and has a row of filaments on each side. A. lanceolatus, the Lancelot, is the only known species. It is a 1 1 
British fish, and an inhabitant of the sea, in which it is found, although very rarely, lurking under stones in !; 
pools left by the ebbing tide. Pallas considered it as a molluscous animal, and not a fish ; but Mr. Yarrell, in his ' 
British Fishes, argues that it is a fish, and that in organization it is the lowest of the class. “ The form of the ( 
fish,” says Mr. Yarrell, “ is compressed ; the head pointed, without any trace of eyes ; the nose rather produced ; 
the mouth on the under edge, in the shape of an elongated fissure, the sides of which are flexible ; from the inner i 
margin extend various slender filaments, which cross and intermingle with those on the opposite side. Along lj 
the sides of the body the muscles are arranged in regular order, diverging from a central line ; one series passing 
obliquely upward and backward, and the other series as obliquely downward and backward ; the anal aperture is ! 
situated one-fourth of the length of the fish in advance of the end of the tail ; the tail itself pointed; from the nose b 
to the end of the tail, a delicate membranous dorsal fin extends the whole length of the back, supported by very j 
numerous and minute soft rays; the surface of the body smooth.” These characters leave no doubt that the | 
animal is a fish ; but that it ought to be classed with the Lamprey family is another matter. The specimen from !: 
which the description was made was not above an inch in length, very slender, and almost transparent.] [ 
