XIII 



PHYLUM CHOEDATA 



219 



This order includes the Sturgeons (Acipenser, Fig. 873, and 

 Scaphirhynchus) found in the rivers of Europe, Asia, and North 



pclj 



FIG. 873. Acipenser ruthenus (Sturgeon), b. barbels ; c. j. caudal fin ; d.j. dorsal fin ; 

 pet. f. pectoral fin ; pv. f. pelvic fin ; sc. scutes ; v. f. ventral fin. (After Cuvier.) 



America ; the curious spoon-billed Polyodon, from the Mississippi ; 

 and Psephurus from the rivers of China. 



ORDER 3. HOLOSTEI. 



Teleostomi in which the paired fins have no basal lobe. The 

 chondrocranium is well ossified by replacing bones and investing 

 bones : branchiostegal rays are present. The vertebral column 



FIG. 874. Lepidosteus platystomus (Bony Pike), c. /. caudal fin \-d.f. dorsal fin; 

 /f. fulcra ; 1. 1. lateral iline ; pet, /. pectoral fin ; pv. f, pelvic fin ; v, f. ventral fin. (After 

 Cuvier.) 



consists of bony vertebrae, and the tail is heterocercal or nearly 

 homocercal. The pelvic fins are abdominal. A reduced spiral 

 valve, a conus arteriosus, and an optic chiasma are present. 



This order includes the Gar-pike or Bony Pike (Lepidosteus, 

 Fig. 874), from the fresh waters of North and Central America and 



FIG. sTf.. Amia calva (Bow-fin). A, the entire animal ; B, ventral view of throat, br. in. 

 branchiostegal nanil rune ; r. f. caudal fin; d.f. dorsal fin ; jvy. pi. jugular plate; pct.f. 

 pectoral fin ; pv. /. pelvic fin ; v. f, ventral fin. (After Giinther.) 



