218 DIVISION I. VERTEBRAL ANIMALS.— CLASS IV. PISCES. 
in common with the P. raber of Europe. The annular or ribbed appear- 
ance of the sides of this fish is owing to the museles, which are endued with 
great streneth, in order to enable it to burrow in the muddy sands of rivers, 
where it penetrates, in a serpentine manner, by means of the snout, the large 
lip of which performs the functions of a terrier. The European species is 
ecnerally taken when the small rivers are cleansed of the superabundant 
sand and mud which obstruct their channels. This last is much sought after 
for food; but the American species is commonly rejected, as is almost every 
animal that either has a real or fancied resemblance to a snake. This fish is 
used for bait.” 
The genera Myxine, Heptratremus, and Grastrobanchus all resemble the 
Lampreys. 
Ampiioxus. — This is a singular creature, and of doubtful character. 
It has the body compressed, the surface without scales, and both ends 
pointed. It has a dorsal along the whole line of the back, but no other 
fins. The mouth is on the under side of the body, opens longitudinally, 
and has a row of filaments on each side. A. /anceolatus, the Lancelet, is 
the only known species. It is 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. Yar- 
rell, in his British Fishes, argues that it is a fish, and that, in organiza- 
tion, it is the lowest of the class. “The form of the fish,” says Mr. Yar- 
rell, “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 elon- 
gated fissure, the sides of which are flexible; from the inner margin extend 
various slender filaments, which cross and intermingle with those on the 
opposite side. Along the sides of the body the muscles are arranged in 
reeular order, diverging from a,central line; one series passing obliquely 
upward and backward, and the other series as obliquely downward and back- 
ward; 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 to the 
end of the tail, a delicate membranous dorsal fin extends the whole length 
of the back, supported by very numerous and minute soft rays ; the surface 
of the body smooth.” These characteristics 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 leneth, very slender, and almost transparent. 
Tue Eyevess Fis or toe MammMora Cave — This curious fish must 
bear some relation to the preceding genus. The following description was 
given to me by the late N. P. Willis : — 
“We reached Lethe, with many stops and occasional drops of encourage- 
