30 PISHES OF ILLINOIS 



Obdee RHOMBOGANOIDEA 



THE GAEPIKES 



Skeleton chiefly bony; Vertebrae separate, simple, with the centra well 

 ossified and opisthocoelous, i. e., connected by ball and socket joints, the 

 concavity of each vertebra being behind; fins without spines; ventral fins 

 abdominal; a cartilaginous mesocoracoid; opercular skeleton complete; 

 maxillary transversely divided into several pieces; air-bladder cellular, lung- 

 like, opening into the dorsal side of the oesophagus. Fresh-water fishes of 

 North America. A single living family. 



Family LEPISOSTEID^ 



the garpikes 



Elongate, subcylindrical fishes with beak-like jaws, and with the ex- 

 ternal bones of the head hard and rugose; body covered with hard, rhombic 

 ganoid plates, imbricated in oblique series; skeleton bony; fins with fulcra; 

 dorsal posterior, nearly opposite anal; tail heterocercal, in the young pro- 

 duced as a filament beyond the caudal fin; gills 4, a slit behind the fourth; 

 no spiracles; an accessory opercular gill (hyoidean hemibranch); pseudo- 

 branch exposed, meeting the hemibranch at an angle on the inner side of 

 the opercle; branchiostegals 3; opercular skeleton complete; nostrils near 

 end of upper jaw; lateral line developed; optic nerves forming a chiasma; 

 premaxillaries forming most of border of upper jaw; maxillary transversely 

 divided into several pieces; both jaws with 2 (or 3) series of conical teeth, 

 the outer smaller; vomer, palatines, and pharyngeals with small rasp-like 

 denticles; tongue toothless, emarginate, free at tip; stomach not csecal; 

 pyloric appendages numerous; spiral valve of intestine rudimentary; air- 

 bladder cellular, lung-like, somewhat functional as a lung, opening into the 

 dorsal side of the oesophagus; arterial bulb with several pairs of valves. 



Garpikes are abundant throughout the Mississippi, Rio 

 Grande, Great Lake, and Appalachian regions, as well as farther 

 southward along the Mexican and Central American coasts and 

 in the fresh waters of Cuba. They are unknown (except as 

 fossils) outside of the limits of the range given, being, as are 

 Amia (the dogfish) and Polyodon (the paddle-fish), one of the 

 characteristic features of the American fauna. But one living 

 genus is known. Fossil garpikes of the genus Lepisosteus and 

 of a related genus (Clastes) have been found in the Eocene of 

 Europe and America. 



