of the pectorals, which appears to be a character of some importance, and which
has led to the generic name of Aplodactylus, amounts in this specimen to six,
being two more than was observed by J\[. Valenciennes in his, though the total
number of rays in this fin is the same. I may also allude to the circumstance of
the dorsal being invested at tlie base with a thickened membrane on each side,
closely covered with small scales, which extends over nearly its whole length,
but is most conspicuous along the spinous portion. This character is not mentioned
by M. Valenciennes. Neither does he mention the rows of minute scales,
which occur between the rays of all the fins, except the ventrals.
Mr. Darwin’s specimen of this fish is eleven inches in length. The following
is the fin-ray formula :
B. 6; D. 15—1/21 ; A. 3,8; C. 17. &c. ; P. 9—v i; V. 1/5.
1. D u l e s A u r ig a . C u v . e t Val.
D ules A uriga, Cuv. et Val. H ist, des Poiss. tom . iii. p. S3, pi. 51.
F o rm .—This species is remarkable for the prolongation o f the third dorsal spine, which, in the
present specimen, is not quite equal to h alf the entire length o f the head and body ; a small
portion, however, appears to have been broken off. The greatest depth is contained three and
a half times in the entire length. The head, measured to the extremity of the opercular
membrane, exactly equals the depth. The line o f the profile is not quite straight, there being
a slight depression at the nape, above which is a convexity in immediate advance of the dorsal
fin. The lower jaw is a very little the longest. The eyes are large ; and the distance between
them barely equals their diameter. The other characters are exactly as stated in the “ Histoire
des Poissons.”
B. 6 ; D. 10/13; A. 3;7 ; C. 17; P. 17; V. 1/5.
Length 5 inches 3 lines.
C o l o u r .—The recent colours are given b y Mr. Darwin in his notes as follows : “ Sides with numerous
waving longitudinal lines of brownish red; the intermediate spaces greenish-silvery, so figured
as to look mottled. Head marked with lines of dull red and green. V entral and anal fins dark
greenish blue.”— He does not notice the vertical bands alluded to by Cuvier and Valenciennes,
which are sufficiently obvious, and which accord with the figure and description of tlie authors
ju st mentioned.
Habitat, Maldonado Bay, Rio Plata,
2. D o l e s L e u c is c u s . Jen.
D ulcs m alo, Val. ? H ist, des Poiss. tom . vii. p. 360.
D . pinxiis caudali, anali, dorsalique molli, nigro-marginatis; dorsali profuudh emar-
ginatá, spind ultima radiis articulatis hreviore; operculo mucronibus duobus, inferiore
máximo, armato; preoperculo margine adscendenti levissimh denticulato, hasali
denticulis fortioribus.
B. 6; D. 10/11; A. 3/12; C. 16, & c .; P. 13; V. 1/5.
L o n g . u n c . 4 . lin . 5.
F orm.— G eneral form resembling that of a small D a c e . Greatest depth about one-third of the entire
length, caudal excluded. Length of the head rather less. Dorsal line falling with the profile
in one continuous gentle curve. Eyes large; their diameter contained two and a half times in
the length of the h e a d : the distance between them less than one diameter. Suborbitals finely
but very conspicuously denticulated. Jaw s nearly equal; the lower one a little the longest. In
each, a band of velutine teeth, with the outer row rather longer than the others. Opercle with
two points, the lower one most developed. Preopercle with the limb striated : the ascending
margin with the denticulations so fine as to be hardly sensible to the naked eye; those on the
basal m argin larger and more obvious. Scales of a moderate size; about forty-three in a
longitudinal row ; their free portions finely striated. Cheeks and opercle scaly; crown naked,
with a shallow groove above each eye. Lateral line at first slightly descendinir, but afterwards
stra ig h t; its course, until past the dorsal and anal fins, a little above the middle of the depth.
Dorsal deeply notched : the anterior portion consisting of nine spines ; the first very short, and
scarcely more than h alf the length of the second; third and fourth longer, increasing g radually;
fifth and sixth equal and longest, equalling half the depth of the b od y ; seventh, eighth, and
ninth, shorter, and gradually decreasing ; the tenth spine, with which the second portion of
the fin commences, is of the same length as the fifth, but not quite so long as the soft rays
which follow; these soft rays, however, gradually become shorter, the last two not more than
equalling the second spinous. The whole space occupied by the dorsal is more than one-third
of the entire length. Anal commencing in a line with the ninth dorsal spine; its own three
spines gradually increasing in length, but the second the strongest; soft portion o f this fin
longer than the corresponding portion of the dorsal, and terminating a little nearer the caudal.
Vent in a line with the seventh dorsal spine. Pectorals small, reaching to the vent. V entrals
attached a little further back, and reaching a very little beyond it. Caudal forked.
C o lo u r.—( I n s p ir its .) Silvery, tinged on the back, and above the lateral line, with bluish grey,
and somewhat mottled in places with darker spots. Fins yellowish-grey, tinged with dusky.
The caudal, anal, and soft portion of the dorsal, are a little mottled with dusky, besides having
a black edging; there is also a conspicuous black spot at the anterior angle of this last fin.