SHARKS AND HATB 



1 i:: 



which, in Bhort, are allied to the Batrachians, and through 

 them with the reptiles, birds, and mammals. All the i 

 e in having a true skull, to which is attached a m 

 ble lower jaw. The brain is well developed and tin 

 is red. Pishes breathe bj gills, which form four archef 



Caudal. 



Anal. Ventral Pertmul 

 Fio. 184.— The Mud-Minnow, with the n . 



each side "f the throat. The body is usually scaled. They 

 are mostly oviparous; some bring fori h their young ali 



Sl B-Cl 18S1 - OF PI8HJE& 



1. Skeleton cartilaginous; 5 i pairs of 



gill-openings 



2. Skeleton cartilaginous «>r bony; 



Bcales often square, enamelled.. G - m, Garpike. 



3. Skeleton bony, of numerous -< p 



arate bones; 4 pairs of gills '/'• Percb, 1 



Sub-Class I. — Elasmobranchii s hians, s irks 



and R ly - 1. 



Those are called Elasmohranchs from the strap-like 

 gill-openings {elasma, strap, and bronchia, gill), 

 sharks, though 6sh-like, are very different from ordi- 

 nary bony fish. Their skeleton or skull is - - El that it 

 can bo cut with a knife, while the tail • • • d, the vi r- 

 tebral column ending in the larger upper lobe. Tin \ 

 have from five to seven gill-openings or slits, whereas tin 

 or perch has but one. The skin is either smooth, or with 

 minute scales, forming - Both jaws are armed 



with numerous sharp, flattened teeth, arra 2 sand 



