ORDER I. CHONDROPTERYGII. “THE LAMPREYS. 217 
It is not known by the fishermen when they return, as they are never seen. 
There is a notion that they all die. They are often seen, in the summer, in 
pairs, at work together, constructing a little mound of stones. They build 
this about three feet in diameter at the base, and about two fect high, of 
stones from the size of an ounce bullet to that of the fist. They often 
aid each other in carrying the same stone. The young go down the river 
when the water begins to freeze. They are then from six to eight inches 
long.” 
The prevailing opinion that these fishes do not return to the sea, but die 
at the end of the season, is, I believe, correct. I have seen them in various 
stages of decay, and in such numbers as to be very disagreeable to bathers. 
The remaining species are P. marinus, two or three feet long, marbled 
with brown, and a yellow ground; P. fluviatilis, silvery, with olive or 
blackish spots on the back; P. planerti, a small river species, eight or ten 
> 
inches long; P. xégricans, the Bluish Lamprey, and some others. They 
are all generally rejected as food in this country, though highly esteemed in 
the Old World. 
Ammocetus. — These fishes have the skeleton so soft and membranous 
that there is not a bone in the whole, not even a tooth; they have the ex- 
ternal form and gill-openings of the Lampreys, but their fleshy lip forms 
only a semicircle on the upper part of the mouth, which is furnished with 
numerous cirri. A. branchialis 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 been 
accused of sucking the gills of other fishes, but perhaps falsely. It is found 
in the sand and mud of small streams; preys on worms, insects, and dead 
matter, and is, in return, preyed on by the eel. 
A. Bicolor. —The Mud Lamprey. This is an American species, found 
in the Connecticut River, and is thus described by Le Sueur : — 
“Dorsal fins low, separated ; the second united with the caudal fin, which 
is rounded; back and sides reddish; abdomen white; the color separated 
by an undulating line. Anterior part of the body sub-cylindric, posterior 
part compressed, and tapering to the tail; nape of the neck clevated; head 
declivous, prolonged into a snout furnished with a lip having two short, 
rounded lobes; these lobes, when the mouth is closed, embrace and conceal 
the lower lip, which is very short; the nostrils are small, and placed in the 
centre of a white oval, pellucid disk, easily movable; on the inside of the 
upper lip, there are small granules, and at the opening of the throat small, 
ramified papille ; the branchial apertures are placed in a longitudinal de- 
pression, oblique and a little curved; the first aperture is above the angle 
of the mouth; on each side of the head there is a whitish spot, which should 
seem to indicate the position of the eyes, that this species is deficient of, 
