272 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



GILL RAKERS 



Next to the structure of tlie scales the iiuinber 

 of gill rakers constitutes the most vahiable char- 

 acter for separating tlie American species. It has 

 been universally so used and its importance justly 

 emphasized. For the three common species of the 

 east coast, figure 1 shows unquestionably that 

 dentatus is distinct from the other two. Fre- 

 quency distributions of all the species studied are 

 shown in tables 2 to 4. The number of gill rakers 

 as recorded may vary somewhat with the observer. 

 For instance, in driitatus the upjiermost gill raker 

 on the upper limb is sometimes very small. Less 



Table 2. — Fmiiirtuij dixlrihiilinii liij vKnihrr of r/il! nikm 

 on till' iiijjjer limb of tlic first gilt arch 



frequently, this is also true of the anteriormost 

 gill raker of the lower limb. In this investigation 

 the smallest gill rakers were included if they were 

 large enough to be manipulated with a dissecting 

 needle. In alhigutta and lethostigina. slight dis- 

 crepancies in the counts made by different investi- 

 gatoi's would be due chiefly to the variability in 

 the uppermost gill raker of the upper limb. This 

 gill raker is sometimes vei-y small, later becoming 

 closely adherent to the gill arch as a triangular 

 piece of cartilage, and finally, seeming to merge 

 with the gill arch. Frequently, when grown to the 



Taulk ."?. — Frcqiiency distribution bij nnmbrr of ijill rnkers 

 on the lower limb of the first gill arch 



1 The short stumps of gill rakers, 3 to 5 in number, on upper limb, not in- 

 cluded in the count. Traces of 1 or more gill rakers in other species also not 

 included (see text). 



' The type specimen has 11 gill rakers on lower limb on eyed side and 13 on 

 blind side, the latter number bt'ing included in the table, all the counts 

 having; been made on the blind side. 



