80 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 
Form.—Still more slender and elongated than the last species. Greatest depth scarcely one-ninth 
of the entire length: head one-sixth. Dorsal and ventral lines very little curved. General 
characters of the head, snout and mouth, as in the A. microlepidota, but the jaws more pro- 
tractile. A row of minute velutine teeth in each jaw most developed above. Eyes moderately 
large ; their diameter nearly one-third the length of the head; the space between them just 
equal to their diameter. Opercle with the posterior margin nearly vertical. Scales larger than 
in the A. microlepidota ; the number of longitudinal rows not exceeding twelve: their form 
different, and rather peculiar, the anterior or free edge of each scale in some instances pre- 
senting two or three processes, separated by deep incisions; in others being irregularly 
notched or jagged, according to the spot whence taken: the surface is marked with con- 
centric lines, but there is no fan of striz on the basal half: the breadth of the scale a little 
exceeds its length, and the basal margin is irregularly sinuous. 
First dorsal answering to the space between the tips of the reclined ventrals and the anal. 
Length of the second dorsal exceeding the intermediate space between it and the first. From 
the end of the second dorsal to the caudal is rather more than one-fifth of the entire length. 
Depth of the caudal fork not exceeding one-third the length of the fin. The anal commences 
in an exact line with the termination of the first dorsal: rather less than its posterior half 
answers to the second dorsal. Pectorals rather long, measuring nearly one-sixth of the entire 
length. Breadth of the silver band one-fourth the depth of the body. 
CoLour.—‘ Body semitransparent, colourless ; with a bright silver band on each side ; also marked 
with silvery about the head.”—-D. The band is remarkably bright, and well defined, much 
more so than in the last species. 
I have ventured to consider this as a new species, though none of the 
specimens in the collection, amounting to three in number, exceed two inches and 
a half in length, and are probably not full-sized. The form of the scales is so 
peculiar, that if it were only the young of some described species, it could hardly 
fail to be identified by such a character, which is not likely to be affected by age, 
nor to have escaped the notice of an observer. Yet I can find none answering to 
it in the “ Histoire des Poissons.” The silvery band also is remarkably bright ; 
though the slenderness of the body, another of its peculiarities, is perhaps due to 
immaturity. The fin-ray formula is somewhat different in the three specimens, 
as shown above, but in other respects they are similar. 
Mr. Darwin's notes state that this species was taken in the month of 
September, in 39°S. Lat., 61° W. Long., several miles from the land. This last 
circumstance, indeed, would seem to indicate that the specimens were not so very 
young, as the fry of most fish keep close in shore. 
Famity.—MUGILID&. 
1. Mucit tiza. Cuv. et Val.? 
Mugil liza, Cuv. et Val. Hist. des Poiss, tom. xi. p- 61. 
Form.—Elongated: the depth contained about five and a half times in the entire length: the head 
