DEVELOPMENT AND LIFE HISTORY OF SOME TELEOSTS 
537 
or crest at the occiput, present in the specimen herein described, and retained by some- 
what larger fish. It may be assumed, therefore, that the ridge is not present in the 
early larvae. This ridge is suggestive of the crest bearing a spine in the young fool 
fishes (Monacanthus). 
Specimen about 4.25 mm long . — Only one specimen of this length is at hand. 
The body remains deep anteriorly, but no longer decreases as abruptly in depth just 
posterior to the vent as in the smaller specimen already described. However, the 
body tapers sharply posteriorly. Its greatest depth is contained 1.7 times in the 
length to the end of the notochord. The head remains deep, with a somewhat more 
sloping anterior profile. Its length is contained 2.9 times in the length to the end of 
the notochord. The snout remains shorter than the eye, and the mouth is quite 
oblique, the gape anteriorly being about on a level with the lower margin of the pupil. 
The maxillary reaches below the middle of the eye. The crest or ridge on the head 
remains prominent, and slightly spinelike. The spines on the preopercular margin 
persist, but are less prominent. The notochord now is bent upward posteriorly, and 
Figube 2i.—-Chaetodiptems faber. From a specimen 2.5 mm long. 
below it are rather well developed rays, forming a moderately long caudal fin, the shape 
of which cannot be determined definitely because of the damaged condition of the fin, 
but it presumably had a round margin as in somewhat larger fish. The spines in the 
dorsal and anal fins are more retarded in development than the soft rays and ca nn ot, 
be enumerated definitely. About 23 soft rays may be counted in the dorsal and 20 
in the anal. The pectoral fins are broken, and the ventral fins appear as mere tufts 
of dermis. 
The preserved specimen at hand is very dark, apparently having become darkened 
by the action of a chemical in the denatured alcohol used. However, black chroma- 
tophores are visible along the side of the abdomen, on the head and back, and at 
midcaudal length. The last-mentioned ones are concentrated and slightly suggestive 
of a cross bar, shown by Ryder (1887, p. 522) for much younger fish, (fig. 25). 
Specimen ,9.0 mm long . — The body remains short and deep and has become some- 
what more robust, the greatest depth being contained 1.8 tunes in the length without 
the caudal fin. The dorsal profile remains quite steep anteriorly, and rather more 
