412 ZOOLOGY. 
girdle is either lyre-shaped or forked, like a bird’s wish-bone, 
curved forward, and with each side connected below; the 
fishes in this respect differing from the Batrachians (Gill). 
The shoulder girdle is usually closely connected by a series 
of intervening bones with the skull, and makes its first ap- 
pearance opposite the interval between the second, and third 
vertebrae. 
The skull and skeleton may be either cartilaginous or bony, 
and the bones of the head and skeleton very numerous. In 
some sharks there are 365 vertebrz ; in some bony fishes 200, 
while in the Plectognathi (fishes like the sun-fishes and Ba- 
listes) there may be no more than fifteen; thus in some 
fishes there may be about one thousand separate bones. No 
fishes have a well-defined sternum or breast-bone, this bone 
appearing for the first time in the Batrachians. The verte- 
bre are almost always biconcave ; this is the simplest, most 
primitive form of vertebra ; it forms a weak articulation, 
admitting, as Marsh states, of free, but limited motion. 
All fishes breathe by gills, which are supported generally 
on four or five cartilaginous or bony supports or arches. The 
gills are never purse-shaped, as in the lampreys, and are 
mostly situated within the head, in front of the scapular arch. 
The mouth is generally armed with teeth varying greatly 
in number and form, and in the bony fishes especially, not 
only the jaws, but any bony projections, such as the palatine, 
pterygoid and vomerine benes, as well as the tongue and pha- 
ryngeal bones may be armed with teeth, so that the food is 
retained in the mouth and more or less torn and crushed be- 
fore being swallowed. 
Fish have no salivary glands. The tongue moves only as 
a part of the hyoid apparatus upon which it is attached. 
After being crushed and torn in the mouth the food passes 
through a short throat or esophagus into the stomach. The 
intestine is generally provided at the anterior end with 
several or numerous ccecal appendages which are especially 
abundant in the cod. The gut is twisted once or twice be- 
fore reaching the vent, but is usually much shorter than in 
the air-breathing Vertebrates, while the vent is placed much 
nearer the mouth than in the tailed Amphibians, thus sepa- 
