30 FISHES OF ILLINOIS 



Order RHOMBOGANOIDEA 



(the garpikes) 



Skeleton chiefly bony; vertebrae separate, simple, with the centra 

 well ossified and opisthoccelous, 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 com- 

 plete; 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, subcvlindrical fishes with beak-like jaws, and with the ex- 

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

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

 fulcra; dorsal posterior, nearly opposite anal; tail heterocercal, in the 

 young produced as a filament beyond the caudal fin; gills 4, a slit 

 behind the fourth; no spiracles; an accessory opercular gill (hyoidean 

 hemibranch) ; pseudobranch 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 devel- 

 oped ; 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 caeca! ; 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 tin- 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 Amid (the dogfish) and 

 Polyodon din- paddle fish), one of tin- characteristic features of the 

 American fauna. Bu1 one living genus is known. Fossil garpikes 



