216 DIVISION I. VERTEBRAL ANIMALS.—CLASS IV. PISCES. 
mental in the sharks and rays, are more developed, and united with each 
other in this family into a kind of cage, but there are no solid gill-arches. 
Instead of being comb-shaped, as in other fishes, the gills have the appear- 
ance 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.” 
Perromyzon. — The Lampreys. They 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. They have strong teeth in 
the maxillary ring, and the inner disk of the lip, which is circular, is cov- 
ered with tubercles, hard and crusted, like teeth. The tongue also, which 
moves backwards and forwards like a piston, and performs the suction, has 
two rows of small teeth. 
P. Americunus. —Le Sueur gives this name to the common Lamprey 
Kel, as it is commonly called, of our rivers. The color of the species varies 
somewhat, being generally an olive brown, of lighter or darker shades. 
“All the upper portion of the body, mottled with dark brown, almost black, 
confluent patches; beneath, of a uniform dull olive. Anterior portion of 
the body cylindrical ; posterior compressed. A slight keel upon the back. 
Head rounded, somewhat flattened on the upper portion in front of the eyes. 
dyes moderate in size; pupils black; irides golden. Distance of the eyes 
from the snout, two inches. A tubular orifice is seen in front of, between 
the eyes, a line in its longest diameter. Seven large branchial apertures 
back of each eye, passing backward in nearly a straight line; the first small- 
est. When this species is unattached, the mouth is a longitudinal fissure. 
When attached, it is circular, the lip forming a ring; within, furnished with 
hard, horny teeth, of a yellow color. Teeth on the roof larger than those 
upon the sides of the mouth; lower margin of the mouth furnished with a 
semicircular row of compact teeth; teeth on the lip small; mucous pores 
obvious in front of the eyes, passing towards the snout, and almost back 
of the eyes. Two dorsal fins; the first commencing back of the middle of 
the body, three inches long, nine inches high. Between this and the second 
dorsal, one inch. Second dorsal, six inches long; more than one inch high 
in its highest part. Anal fin, a mere fringe. Caudal fin appears like the 
extremity of the solid portion of the body, very much compressed.” 
This fish is about two feet in length at maturity, and weighs from three 
to four pounds. In the spawning season, it ascends our various rivers, and 
IT have seen it, in countless numbers, far in the interior of Maine, building 
its mounds of stone in the clear streams. According to Dr. Bartlett, “ they 
ascend the rivers a little earlier than the shad, and move mostly in the night. 
