is larger still, and sometimes weighs upwards of a 
thousand pounds. In the spawning season, it ascends 
the Volga and other large rivers, where it is speared, 
or taken in strong, nets. 
Plate XI. fig. e. Actpenser ruthenus, the Sterlet, 
rene 
Cartilaginous fishes with large pectoral and 
ventral fins, usually with the mouth transversely 
opening below the projecting snout. Five gill-open- 
ings (rarely one) on each side, without gill-covers. 
They are marine fish, but are sometimes seen in 
estuaries. 
Family I. Carchariide#. The Sharks have a 
long tapering body, erect dorsal fins, and a large 
fleshy tail. The eyes have well-formed lids, and 
the mouth is furnished with several rows of large 
sharp teeth. The larger species grow to the length 
of thirty feet. 
Plate IX. fig. a. Carcharias vulgaris, the com- 
mon Shark, is found in all seas, and is an excellent 
swimmer, which will follow the swiftest vessel for 
days, feeding on any offal which may be thrown 
overboard, and not unfrequently devouring men, if 
they fall into the water. The skin is as rough as 
a file, from embedded calcareous particles, and is 
called shagreen. The liver yields excellent oil. 
Plate IX. fig. b. Zygena malleus, the Hammer- 
headed Shark, is also a formidable creature, which 
grows to the length of nine feet or more, and is as 
voracious as a shark. Its head has two lateral ex- 
pansions, at the ends of which the eyes are fixed, 
and the snout is truncated. It is found in the 
Atlantic Ocean and in the Mediterranean. 
Plate IX. fig. c. Prist’s antiquorum, the Saw- 
fish, is a still stranger-looking fish than the Hammer- 

measures less than four feet in length, and does not 
exceed thirty pounds in weight. It is found in the 
seas and rivers of Eastern Europe, and is more 
| highly esteemed than the larger species. 
Selachii. 
head. It has a powerful weapon on the form of a 
long flattened saw-like extension of the upper jaw, 
with which the Saw-fish does not fear to attack the 
largest monsters of the deep. The Saw-fishes inha- 
bit tropical seas. 
Family Il. Raiide. In the Rays the body is very 
broad and depressed, with the eyes on the depressed 
surface, and the mouth and gill-opening beneath. The 
breadth of the body is increased by its expanding 
into the pectoral fins. The teeth are broad, obtuse, 
and arranged like paving-stones. These fish swim badly, 
and generally rest at the bottom of the sea. Some 
species can give an electric shock. 
Plate X. Fig. a. Myhobatis aguila, the Eagle 
Ray, has a long saw-like spine at the end of the tail. It 
is more common in the Southern Seas than in ours. 
Plate X. fig. c. Raza clavata, the Thornback 
Skate, is common in the Northern Seas. It derives 
its name from the numerous spines scattered over 
its body, and even between the eyes and the snout. 
Plate X. fig. b. Torpedo marmorata, the Tor- 
pedo, is commoner in the Mediterranean, and other 
warm seas, than in those of Northern Europe. The 
tail is short, the naked body nearly round, and the 
teeth are small and sharp. The electric organ is 
situated between the pectoral fins and the head, and 
consists of numerous vertical quadrangular or hexa- 
gonal prisms, filled with a sort of jelly, and traversed 
by large branching nerves. 

Order Ill. Cyclostomi. 
These are cartilaginous fishes of a very low grade, 
with cylindrical bodies, no pectoral nor ventral fins, 
a ring-like sucking mouth, and fixed gills, without 
gill-covers. They live in both salt and fresh water, 
and are in part parasitic on other fish, to which they 
fix themselves. 
Family I. Petromyzide. The sucker-like mouth 
is formed either of a single round toothed lip, or of 
two unequal toothless lips. There are seven gill- 
openings on each side of the neck, which were for- 
merly supposed to be eyes. Most of the species live 
in clear streams under stones; but a few are marine. 
Plate X. fig. d. Fetromyzon marinus, the Lam- 
prey, which sometimes measures three feet in length, 
is common on the coasts of Europe, but comes into 
rivers to spawn. It is green marbled with brown on 
the back and sides, and the belly is white. It has 
a round toothed snout, with which it can fix itself 
very firmly to rocks, 
Plate X. fig. e. Petromyzon fluviatilis, the Lam- 
pern is dark green on the back, with yellowish sides, 
and white beneath. It grows to the length of about 
eighteen inches, and is very common in rivers, where 
it spawns among stones in spring. 
Plate X. fig. f. Fetromyzon Planerz, the Small 
Lampern, is likewise a common river fish but is much 
smaller, hardly exceeding a foot in length. It is olive- 
green, and differs from the other species in the con- 
tinuous dorsal fin. 
Plate X. fig. g. The immature form of the last 
fish is known as the Mud Lamprey, and was formerly 
considered to belong to a distinct genus, being called 
Ammocates branchialis. \t is a wormlike creature, 
about six inches long, and likes to attach itself to 
the gills of other fish. It lives in muddy brooks, and 
fishermen sometimes use it for bait. 
Family IH. Myxinida. These are small parasitic 
fish, without lips. 

Order IV. Leptocardii. 
The Lancelet (Branchiostoma lanceolatum) is a 
small creature about three inches long, without pec- 
toral or ventral fins, brain, skull, or heart, the place 
of the latter being supplied by pulsating vessels. Se- 
veral recent authors do not regard it as a fish at 
all, but place it in a class, by itself, or even as the 
type of a distinct subkingdom from the Vertebrata. 
