SYSTEMATIC 

 ARRANGEMENT OF FISHES. 



CLASS XIV. 

 FISHES. 



VERTEBRATE animals breathing during the whole life by per- 

 sistent branchiae, having cold blood and a ventricle of the heart 

 single, branchial alone ; aquatic, mostly oviparous. 



I. Organ of smell unpaired. 



SECTION I. Dermopterygii. 



Fins surrounding the body at the back and abdomen with a 

 cutaneous border: pectoral and anal fins none. Dorsal cord per- 

 sistent, in place of a vertebral column. (Swimming-bladder none. 

 Ribs none.) Body covered by a soft skin, not scaly. 



ORDER I. LeptocardiL 



Pulsating vessels in place of heart. Blood pale. Branchial sac 

 in front of oesophagus, included in the cavity of body. 



Family I. Amphioxini. (Characters of the order those of the 

 single family.) Body compressed. 



Amphioxus YARRELL (Branchiostoma COSTA). Body acuminate 

 at both ends ; dorsal fin extended at the back through the whole 

 length, confluent at the tail with the anal. Mouth inferior, pre- 

 senting a longitudinal fissure, furnished with somewhat rigid cirri 

 (12 15 on each side). 



This genus of fishes is the most imperfect of the typus of verte- 

 brate animals. There is no brain present, at least not as a distinct 



