PHYLUM CHORDATA 



219 



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

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



/"=«/ 



Fig. SY3.— Acipenser rutlienus (Sturgeon), i. barbels; c. j. caudal fln; rf.j. dorsal fin ; 

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



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

 and Psephuncs from the rivers of China. 



OrDEE 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 



/-vr 



Fig. 874.— Lepidosteus platystomus (Bony Pike), e. f. caudal fln ; d. f. dorsal fin ; 

 €. fulcra ; 1. 1, lateral dine ; pet. f. pectoral fln ; 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 876 — Amia calva (Bow-fin). A, the entire animal ; B, ventral view of throat, br. m. 

 branchiostegal jncmirane ; c. f. caudal fin ; d.f. dorsal fin ; jvff. jjl. jugular plate ; jact.). 

 pectoral fin ; jiv. f. pelvic fln ; v. f, ventral fln. (After GUpther.) 



