202 FISHES OF ILLINOIS 



ORDER HAPLOMI 



PIKE-LIKE FISHES 



Skeleton bony; anterior vertebrae distinct, without Weberian ossicles; 

 ventral fins abdominal, rarely wanting; all fins soft-rayed, although the first 

 dorsal ray is in a few form somewhat stiffened and spine-like; no adipose fin; 

 pectoral arch suspended from the skull; mesocoracoid wanting (this character 

 constituting the only important distinction between these fishes and the 

 Isospondyli); opercular bones well developed; air-bladder with a distinct 

 duct. Four families; species numerous and widely distributed, chiefly in- 

 habiting fresh or brackish waters of both hemispheres. 



KEY TO FAMILIES OF HAPLOMI FOUND IN ILLINOIS 



a. Vent normal, not far in front of anal fin; eyes normal. 



b. Lateral line present; jaws duck-bill-like Esocidae. 



bb. Lateral line wanting. 



c. Upper jaw not protractile Umbridae. 



cc. Upper jaw protractile (the upper lip separated from the skin of the forehead 



by an evident groove, which passes wholly across the muzzle) 



Poeciliidse. 



aa. Vent jugular, in front of pectorals and close 'behind gill-openings; eyes more 

 or less concealed by thick skin; ventrals ordinarily wanting, or much 

 reduced Amblyopsidae. 



FAMILY UMBRIDAE 



THE MUDFISHES 



Body oblong, broad anteriorly and compressed behind; head somewhat 

 flattened; scales cycloid, covering head and body; lateral line wanting; 

 skeleton osseous; anterior vertebrae simple; no spines in fins; ventrals ab- 

 dominal; dorsal fin posterior; caudal rounded; no mesocoracoid; gill-mem- 

 branes little connected; branchiostegals 6 to 8; pseudobranchiae hidden, 

 glandular; gill-rakers little developed; mouth moderate, premaxillary not 

 protractile; lateral margin of upper jaw formed by the maxillaries, which are 

 toothless and without distinct supplemental bone; premaxillaries, lower jaw, 

 vomer, and palatines with bands of villiform or cardiform teeth, stomach 

 without blind sac; no pyloric caeca; air-bladder simple, with distinct duct; 

 oviparous fishes. 



