106 CLASS-BOOK OF ZOOLOGY. 



SECTION XXV. 



IV. ICHTHYOLOGY. 



§ 443. Ichthyology is the science which treats of Fishes ; 

 and forms the fourth class in the Animal Kingdom. 



§ 444. Fish, like Reptiles, have cold red blood ; they 

 live in water, breathe by means of gills, are provided 

 with fins instead of feet for executing their motions, and 

 are oviparous. 



§ 445. The fins consist of several rays connected by 

 a tender membrane,, and, according to their position, have 

 five different names, viz. : Dorsal, Pectoral, Ventral, Anal, 

 or Caudal. 



§ 446. Dorsal fins are those which are situated upon 

 the back, (Pinnae dorsales.) 



The Pectoral fins are situated on both sides, near the 

 gills, (Pinnae pectorales.) 



Ventral fins are those which are situated beneath, on 

 both sides before the anus, (Pinnae ventrales.) 



The Anal fin is that which is situated beneath, near 

 the tail, (Pinna analis.) 



The Caudal fin is situated at the extremity of the 

 body, and constitutes the tail, (Pinna caudalis.) 



§ 447. The Gills (Branchiae) are the breathing organs, 

 and consist of arched rays, usually four on each side. 



\ 448. The teeth with which Fishes are provided, are 

 usually found in the jaw ; but sometimes on the tongue, 

 in the palate, and also in the throat. They are used as 

 weapons of attack and defence. 



\ 449. Fishes are provided with various means of de- 

 fence and attack. Some are armed with bristles, as the 

 Sea-porcupine ; others with a sting, as the Cat-fish ; others 

 again with a sword, as the Sword-fish. Some also are 

 provided with a saw, as the Saw-fish ; and others with 

 an electric benumbing power, as the Electric Eel. 



\ 450. The frame of Fishes is cartilaginous or bony. 

 The back-bone goes the whole length of the body, and 



