OBSERVATIONS ON FISH SCALES. 
143 
Order ACANTHOPTERI. Spiny-rayed fishes. 
THE ACANTHOPTERYGIAN TYPE OF SCALE. 
The serranid Ceniropristes striatus (Linnaeus), the black sea bass, from Woods Hole, Mass., may 
be taken as a type for the definition of the acanthopterygian scale. This scale is more or less quadrate, 
with the nucleus subapical, the basal circuli fine and transverse, the basal radii strong, spreading out 
like a fan, and the apical area covered with fine dentiform structures which can 
be coimted in rows obliquely or transversely, and on tlie margin form a series of 
fine teeth. The Ceniropristes scale described is atypical in one respect — the 
marginal teeth are truncate instead of pointed. The toothed or ctenoid feature 
appears to be derived from the longitudinal apical circuli which become modi- 
fied and segmented, the terminal segments especially taking the form of teeth. 
It is this segmentated arrangement which gives the apical area in acanthop- 
terygians its special character, resembling very much tlie arrangement of bracts 
in the heads of some composite flowers. In the pceciliid scale we have a 
structme resembling much that of the acanthopterygians, but the ctenoid char- 
acter wholly undeveloped ; in some cichlids we attain a superficially similar 
condition, the ctenoid character having been lost. 
At first sight the scales of the various acanthopterygian families Hasmulidae, 
Lobotidas, Serranidae, Lutianidae, PercidsejCentrarchid®, Anabantidae, Sciasnidae, 
Mullidas, Polynemidae, and Mugilidae appear so much alike that classification 
seems extremely difficult. There are, however, some good distinctions visible 
on close comparison and brought out more or less in the following table. This does not apply to 
latinucleate or lateral line scales. 
Basal margin broadly emarginate in middle, the basal radii (about 4 or 6 distinct) nearly parallel, 
converging toward the margin; teeth of apical margin very small, not different from the sub- 
marginal structures Mugil curema Cuvier & Valenciennes (Mugilidse) 
Basal radii spreading i 
1. Middle of basal margin deeply emarginate; radii one in the middle, and usually three (closer 
together than the innermost to the middle one) on each side, not deeply impressed; apical 
modified area reaching nearly to nucleus; apical marginal teeth very small, sharp; sub- 
apical pattern composed of elements resembling phalanges, but grooved or bicarinate.“ 
Polydaciyhis octonemus Girard (Polynemidae) 
Basal margin deeply lobed between the five of six widely and often irregularly spaced basal radii; 
large scales with extremely fine circuli; modified marginal area not approaching nucleus; 
marginal teeth sharp; submarginal elements phalangiform, flattened, looking like bricks 
placed on end, without grooves or keels, though some of the basal ones may have broken ver- 
miform markings. Surmullets (Mullidae) 2 
Not like the above (in Perea the basal margin is strongly lobed, but then the basal radii are regular 
and very deeply impressed, and the apical region is differentiated into two parts) 4 
2. Subapical marginal elements longer, many about four times as long as broad. 
Mulhis anratus Jordan & Gilbert, Woods Hole, Mass. 
Subapical marginal elements shorter, none about four times as long as broad 3 
3. Elements of apical area in 5 or 6 transverse rows (only two in latinucleate scales). 
Upeneus dentatus Gill. Clarion Island (Albatross) 
Elements of apical area in 8 or 9 transverse rows. 
MuUoides samoensis Gunther. Honolulu, Hawaii (Jordan & Evermann) 
4. Apical area beset with linear, spine-like structures (the marginal teeth not differing), the lateral 
ones often continuous at base with the circuli; apical circuli very widely spaced, meeting 
at about a right angle above nucleus; basal radii about 15 (Anabantidae). 
Anabas scandens Linnaeus. Lake Buhi, Philippine Islands 
Apical area not thus 5 
5. Scales conspicuously longer than broad; margin with about 7 or 8 prominent teeth or projections, 
to the ends of which the basal framework of the scale is carried; apical area with much 
reddish brown pigment; scale suggestive of Achirus, but the subapical structure different. 
Epinephelus niveaius (Cuvier & Valenciennes). Katama Bay, Mass. (Serranidae) 
Apical margin with many teeth 6 
Fig. 8. — Ceniropristes stri- 
atus (Serranidae). Cte- 
noid structures. Bureau 
of Fisheries. 
“ In Mu^il these structures are dentiform, like pointed scales, thus very different. 
