Order VIII. Haplomi. 



THE PIKE-LIKE FISHES. 



Anterior vertebrae simple; mesocoracoid wanting; the coracoids 

 normally developed; opercular bones, well developed; ventral fins 

 abdominal; pectoral fins placed low; dorsal fin more or less posterior, 

 the first ray sometimes stiffened and spine-like; no adipose fin; head 

 usually covered with cycloid scales like those on the body ; mouth with 

 teeth. Fishes chiefly inhabiting fresh water. 



Family XI. Poeciliidw. 



THE KILLIFISHES. 



Body elongate, or deep and compressed behind, depressed forward, 

 and covered by rather large cycloid scales; head scaly, at least 

 so above; mouth terminal, small, lower jaw usually the longer; pre- 

 maxillaries extremely protractile ; teeth conical, or incisor-like, usually 

 confined to the jaws, sometimes on vomer; lower pharyngeals separ- 

 ate, with cardiform, rarely molar teeth; gill membranes somewhat 

 connected, free from the isthmus; gill rakers very short and thick; 

 branchiostegals 4 to 6; pseudobranchiae none; dorsal fin single, behind 

 the middle of the body; caudal fin not forked; ventral fins abdominal, 

 rarely absent; air bladder, if present, simple. 



The species of this family are usually of small size, some are ovip- 

 arous, others viviparous. In the oviparous forms, the males and 

 females are more nearly alike in size and color, and the anal fin of 

 both sexes is similar in form and position. In many of the viviparous 

 species the anal fin of the male is placed well forward and modified 

 into an intromittent organ, and the male is about half the length of 

 the female. In other viviparous forms the anal fin of the male has 

 the same position as that in the female, but differs from it in having 

 the first five or six rays short and stiff, and separated from the rest of 

 the fin by a shallow notch ; the sexes differ in color, but are of about the 

 same size. In some species the alimentary canal is about as long as 

 the fish; in others it is several times as long. 



KEY TO THE GENERA OF PCECILIIDvt. 



a. Intestinal canal comparatively short, little 

 convoluted, usually less than one and one-half 

 times the total length of the body (2 in Chap- 

 alichthys) ; teeth little movable ; dentary bones 

 firmly united; species chiefly carnivorous. 



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