OBSERVATIONS ON FISH SCALES. 
H7 
lines, so as to seem segmented. In S', borealis DeKay, from Woods Hole, the colorless scales have a 
diameter of hardly mm., and the fine radii, instead of continuously interrupting the circuli, are 
represented by series of minute round holes, which, however, coalesce in some places, producing a 
condition like that of the great barracuda, S', picuda. In the northern barracuda, S. borealis, the apical 
sculptureless area is very small or wanting. The sphyraenid scale is very suggestive of that of Gadus 
and allied genera. 
A'*'A A 
•A,-.; a: a 
A >'.yv A 
A >A 
A A 
Fig. 9. —Mugil (Mugilidae). Cte¬ 
noid area. Bureau of Fisheries. 
Fig. 10. —Sphyrcena borealis (Sphyraenidae). Sculpture. 
Bureau of Fisheries. The transverse strands are circuli. 
Jordan & Evermann state that the families Atherinidae, Mugilidae, and Sphyraenidae are closely 
related (Bulletin 47, U. S. National Museum, pt. 1, p. 788). They were associated together in the 
order Percesoces by Cope. Boulenger includes in Percesoces several other families, as Anabantidae, 
Stromateidae, Polynemidae, Scombresocidae, etc., stating that the group is perhaps only an artificial 
one, but “a gradual passage may be traced connecting the most aberrant types.” 
The scales would certainly suggest that the three families described above are not very closely 
related. 
Suborder Rhegnopteri. 
POLYNEMIDAE. Threadfins. 
Jordan states that the Polynemidae are allied to the Mugilidae, but differ from them and from all 
other fishes in the structure of the pectoral fin and its basal bones. In Boulenger’s arrangement they 
go in the Percesoces, following the Mugilidae. In Polydactylus octonemus Girard the scale is quite 
Fig. ii .—Polydactylus (Polynemi¬ 
dae). Apical teeth. Bureau of 
Fisheries. 
typically Acanthopterygian, with ctenoid apical area, nucleus apicad of middle, and well-developed 
basal radii. The scale is nearly as in Mugil, having the same basal emargination, but differing in the 
spreading basal radii. The minute elements of the apical area are not as in Mugil, the submarginal 
ones being truncate instead of pointed. 
Although there are differences, the scales would suggest that the Polynemidae are actually nearer 
to the Mugilidae than the latter to the Atherinidae or especially the Sphyraenidae. 
