RUDDER FISHES IN THE WESTERN NORTH ATLANTIC 



473 



NUMBER OF 

 DORSAL SOFT- RAYS 



FiGDRE 20. — Comparison of number of dorsal and anal soft-rays on 214 specimens of Kyphosus from the North Atlantic 

 Ocean. Solid lines, enclosing s.'s, denote K. sectalrix; dashed lines, enclosing i.'s, denote K. incisor. 



geographical ranges of both species, but distinct 

 within much of the region intensively studied. 

 In K. sectatrix 70 percent had 18 rays, 23 percent 

 had 19 rays; in K. incisor 82 percent had 19 rays. 

 Eightj'-four percent of the specunens of K. 

 sectatrix taken at Bermuda, the Bahamas, and in 

 the Antilles Current had 19 rays, the normal 

 count for K. incisor; 83 percent of those taken 

 along the Atlantic coast of the United States 

 had 18 rays (table 4). This indicates a popula- 

 tion of K. sectatrix, m the Bahama-J^ennuda 

 region, distinct from the population found along 

 the Atlantic coast of the United States. Soft-rays 

 start branching in K. sectatrix by 15.4 mm. (in 

 8 rays) ; in K. incisor branching begins after 

 15.8 mm. 



Pelvic fin. — No interspecific or intraspecific 

 variations in the pelvic fin were observed. 



Caudal fin. — No interspecific or intraspecific 

 variations were observed in the principal caudal 

 raj's. In the dorsal lobe of the caudal fin, two K. 

 sectatrix longer than 15 mm. had 9 secondary raj^s; 

 two K. incisor more than 15 mm. had 10 secondary 

 rays. Since secondar}- raj-s were counted only 



on sLx cleared and stained specimens (4 longer 

 than 15 mm.), the value of this character for 

 distinguishing the two species is questionable. 



Gill rakers. — Numbers of first-arch gill rakers 

 were good characters for separating K. sectatrix 

 from K. incisor (fig. 21). On the entire first arch 

 of specimens more than 16 mm., 96 percent of the 

 K. sectatrix had 22 to 25 gill rakers, while 90 

 percent of the K. incisor had 26 to 31 gill rakers. 

 On the upper limb of first arch of specimens 

 above 16 mm., 67 percent of the K. sectatrix had 

 6 gill rakers, and 29 percent had 7 gill rakers; 

 19 percent of the K. incisor had 6 gill rakers and 

 80 percent had 7 or 8 gill rakers. On the lower 

 limb of first arch of specimens above 16 mm., 92 

 percent of the K. sectatrix had 17 or 18 gill rakers; 

 75 percent of the K. incisor had 20 or 21 gill 

 rakers. On the ceratobranchial bone, including 

 all sizes, 91 percent of the K. sectatrix had 12 or 



13 gill rakers; 95 percent of the K. incisor had 



14 or 15 gill rakers. 



Scales. — Interspecific variation in number of 

 scales was indistinct throughout the geographical 

 ranges of both species, but distinct within much 



