DEVELOPMENT AND LIFE HISTORY OF SOME TELEOSTS 
601 
10 mm long. The difference in the depth of the body is somewhat more evident than 
in smaller fish, H. hentz being notably deeper and also somewhat stockier. The much 
longer preopercular spines, particularly those at the lower posterior angle in H. hentz, 
too, are useful in separating the species. Another helpful difference is found in the 
shape of the dark dots at the base of the anal, which have become elongate and form 
lines in II. geminatus, whereas they are round in II. hentz. 
Specimens about 12 mm long. — The body has increased somewhat in robustness 
since a length of 10 mm was reached, but it remains much more slender than in speci- 
mens of Hypsoblennius hentz, of this size, the depth being contained in the length 
without the caudal fin 4.4 to 4.75 times. The forehead is strongly convex, but not 
vertical; the snout projects quite prominently, being fully three-fourths as long as the 
e} 7 e; and the mouth is terminal and only slightly oblique, with the tip of the lower 
jaw scarcely above the level of the lower margin of the eye. A low bony ridge, evident 
over the eye in somewhat smaller specimens, is scarcely visible now and the inter- 
orbital remains strongly convex. Minute preopercular spines remain present and do 
not seem to have either increased or decreased in proportionate length since the fish 
attained a size of 10 mm. A small fleshy tentacle, notably shorter than the pupil, 
is visible over the eye for the first time. The dorsal spines, as in the adult, are shorter 
than the soft rays of that fin; the caudal fin has a nearly straight margin; and the 
ventral fins have increased in proportionate length, being almost twice as long as the 
eye. Pigmentation remains virtually as in the smaller fish described in the preceding 
paragraph (fig. 108). 
Hypsoblennius hentz is distinguished from the present species at this size (as in smaller 
fish) by the vertical forehead, the slightly inferior horizontal mouth, the prominent 
bony ridge over and in advance of the eye, by the much larger preopercular spines, and 
by the greater amount of black color on the pectoral fins. 
Specimens 15 to 16 mm long. — Specimens of this size are very similar in shape 
to the adult, and they have the appearance of being much older fish than 12- or even 
14-mm specimens. The body has become deeper and more robust, the depth being 
contained in the length, without the caudal fin, 3.3 to 3.6 times. The snout projects 
rather prominently in advance of the forehead and it is nearly or quite equal to the 
length of the eye. The small mouth is now wholly below the level of the lower margin 
of the eye. It is almost horizontal, as in the adult. The lower jaw is slightly shorter 
than the upper one and the maxillary scarcely reaches beyond the anterior margin 
of the pupil. Preopercular spines, present in somewhat smaller specimens, are not 
evident. Three or four fleshy tentacles, placed close together and in a transverse 
row and rising from a common base, are present over each eye, the longest one being 
about as long as the pupil. Another fleshy tentacle is present behind the nostril. 
The fins are all shaped virtually as in the adult. The color cannot be fully described, 
