LEPIDOSIREN. 557 



ventral, and the right the dorsal aspect of the lungs. In regard to the 

 veins, there is a single true postcaval, or inferior vena cava, along with 

 a persistent left posterior cardinal. There is a single caudal vein giving 

 rise to a right and left renal portal. Two pulmonary veins unite near 

 the front of the lung in a single vessel, which enters the left side of the 

 auricle. 



Lepidosiren.--This mud-fish from the Amazons has an eel- 

 shaped body, with a continuous vertical fin. The limbs are 

 reduced to the axis only. There is a well-developed septum 

 in the auricle, an all but complete septum in the ventricle, 

 and a complete septum in the conus. The lung is double. 

 The eggs are laid in burrows, and the male remains curled 

 up beside them. The young are hatched with external 

 gills. The air-bladder or lung is double, and its relations 

 to blood vessels are like those in Protopterus. 



