FOURTEEN TELEOSTEAN FISHES AT BEAUFORT, N. C. 
421 
Figure 44. — Leiostomus xanthurus. From a specimen 7 millimeters long 
the base of the dorsal also. The bases of a part of the rays are becoming evident 
as pale and slightly protruding areas. No changes in color worthy of note have 
taken place since a length of 3.6 millimeters was attained. 
Specimens 7.0 millimeters long. — At this size the anal fin occasionally is well 
enough developed to show the anal rays, or at least the articulations between the 
rays and the interhsemal spines generally are evident, appearing as somewhat elon- 
gate, rectangular pale areas, surrounded by a dark line. (The prominence of these 
markings appears to depend partly on preservation, as in some lots they are uniformly 
more distinct than in others.) It often is possible to get a fairly accurate count of 
the rays from these sutures eveft though the rays themselves are not evident. The 
dorsal fin generally is some- 
what less definitely devel- 
oped than the anal, and the 
spinous portion is still miss- 
ing. The pectoral and ven- 
tral fins are just becoming 
visible, being short and with- 
out definite rays. The hind 
gut no longer projects prominently. However, a large space, with only a semitrans- 
parent membrane, remains between the vent and the origin of the anal. This area 
exceeds in length the diameter of the eye. The notochord is still evident and its 
extremity is visible in the fin membrane above the base of the uppermost ray of the 
caudal. The spinal column, too, is visible on the median line of the side at the base 
of the caudal. Pigmentation now consists of a dark spot at the articulation of the 
mandible ; the dark peritoneum above the viscera (very evident in smaller specimens) 
is still rather faintly visible through the abdominal wall; a dark chromatophore re- 
mains at a point slightly in advance of the origin of the anal; other pigment spots 
are situated along the ventral edge, as in smaller specimens. (Fig. 44.) 
Specimens 10.0 millimeters long. — The anal spines and rays are quite fully 
developed, and an accurate count can be made under proper magnification and 
illumination. The soft 
dorsal is well developed, 
except posteriorly where 
the rays are very short 
and indefinite. Although 
a variation in the prog- 
ress of development ex- 
Figure 45. — Leiostomus xanthurus. From a specimen 11 millimeters long ists the base of the Spi 
nous dorsal usually is evident only as a thickened membrane and generally no spines, 
as yet, are evident. The middle rays (about 10) of the caudal fin are all of nearly 
the same length, making the posterior margin of the fin straight. (In smaller speci- 
mens the margin is round.) The pectorals and ventrals are short but have definitely 
differentiated rays. The mouth is much less oblique than it is in smaller specimens 
and it is slightly inferior, approaching in both respects the position it has in the adult. 
The heterocercal character of the tail — that is, the upward bend in the notochord, 
prominent in somewhat smaller specimens— scarcely is discernible. Pigmentation 
has undergone no changes worthy of note. (Fig. 45.) 
Specimens 15.0 millimeters long. — The changes in development in fish of this 
length and those 10 millimeters long are not pronounced. The first dorsal now has 
