6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 10^ 



named occur in southern Florida, indicating that suitable conditions 

 for their welfare do not exist there. Hence, the separation of the At- 

 lantic and Gulf representatives is complete. Under this separation, 

 and under the influence of a different environment, the fishes named 

 seem to have become sufficiently differentiated to constitute distinct 

 species. 



KEY TO THE SPECIES 



a. Scales relatively large, fairly regularly placed, 35 to 56 oblique series 

 crossing middle of side ; body rather elongate, its greatest depth 30 to 40 

 percent of the standard length. 

 b. Scales on back and at base of caudal much smaller than those along middle 

 of side; ventral fin with a definitely convex margin; the innermost ray 

 more than two-thirds length of the outermost one, the fin not pointed 

 when folded; upper part of opercle with prominent radiating striae; 

 shoulder spot followed by a variable number of smaller dark spots in 

 adults. 

 c. Ventral outline of body anteriorly moderately convex ; usually only 

 about half the greatest depth below a straight line extending through 

 lower margin of eye to middle of base of caudal ; sheath of scales at 

 base of dorsal fin low, composed for the most part of a single row of 

 scales, covering only the basal third of the longest rays when stand- 

 ing erect ; pectoral fin rather short, falling far short of reaching base 

 of ventral fin, 3 to 7 vertical series of scales between its tip and base 

 of ventral, the fin with 16 to 18 (rarely 15) rays. 

 d. Maxillary long, reaching well beyond vertical from posterior margin 

 of pupil, 13 to 16 percent of standard length; mandible long, 16 to 

 19 percent ; pectoral fin moderately long, failing to reach base of 

 ventral fin by less than diameter of eye, 3 or 4 vertical rows of 

 scales between tip of pectoral and base of ventral, its length 17 

 to 21 percent of standard length ; caudal fin moderately long, the 

 lower lobe about as long as head, 25 to 35.5 percent of standard 



length tyrannus, p. 7 



dd. Maxillary shorter, reaching only to vertical from posterior margin 

 of pupil, 12 to 13 percent of standard length; mandible short, 15.5 

 to 16 percent ; pectoral fin short failing to reach base of ventral 

 fin by a distance exceeding diameter of eye, 5 to 7 vertical series 

 of scales between its tip and base of ventral, its length 15.5 

 to 16 percent of standard length ; caudal fin very short, the 

 lower lobe shorter than head, 22.5 to 25 percent of standard 



length brevicaudata, p. 10 



cc. Ventral outline of body anteriorly strongly convex ; much more than 

 half the greatest depth below a straight line extending through 

 lower margin of eye to middle of base of caudal ; sheath of scales at 

 base of dorsal fin much higher, composed for the most part of two 

 rows of scales, covering basal two-thirds of shortest rays when 

 standing erect; pectoral fin longer, often nearly reaching base of 

 ventral fin, seldom more than i or 2 vertical series of scales between 

 its tip and base of ventral, the fin with 14 to 17 (usually IS or 16) 



