PROTOPTERUS. 



555 



The heart has only one auricle, with a dorsal fibrous ridge hinting at 

 a division. A similar incomplete septum occurs in the ventricle, 

 and the sinus venosus is divided into a left pulmonary and a right 

 systemic portion. The conus arteriosus is peculiarly twisted, and 

 contains a short longitudinal spiral valve and numerous large 

 "pocket" (or "Ganoid") valves. 



Protopterus. - - This mud - fish lives in the Gambia, 

 Quilimane, and some other African rivers. It is mainly 

 but not exclusively carnivorous, and attains a length of 

 2 to 3 ft. It has extraordinary vitality, surviving severe 



sn.t. 



e.b 



PC.L 



FIG. 270. Head region of Protoptcnis. From \V. N. Parker. 



sn.t., Sensory tubes ; /./., lateral line ; c.br. , external gills pc.l. , 

 pectoral fin ; op. , operculum. 



wounds, long fasting, and desiccation. It appears to be 

 most active at night, and to prefer shallow water, swimming 

 rapidly with powerful tail-strokes, or "walking" slowly 

 along the bottom with its filamentous fins moving alter- 

 nately on each side, somewhat like the legs of a newt. At 

 short intervals it comes to the surface to take mouthfuls of 

 air, which passes out again through the opercular aperture. 



As the dry season approaches, Protopterus burrows into the earth to 

 a depth of about 18 in., coils itself up, and secretes abundant mucus 

 from its skin glands. This secretion forms a cocoon or capsule, \\ ith 



