I
u n i
C o lo u r.— (/ii spirits.) Greenish-brown, with numerous conspicuous spots and small irregular
transverse bars of black. U nder a lens the spots appear to be made up of thickly crowded
black specks upon a dark brown ground ; the bars result from some of the spots being oon-
flnent. The belly appears to have been white. T he rays of ah tbe fins are dotted with dusky,
but the membranes transparent and colourless.
T he individual described above was taken by Mr. D arw in in a fresh-water
brook, in H ardy Peninsula, T ierra del Fuego. H is collection, however, contains
four other specimens found in stream lets and creeks Itigh up the river of S anta
Cruz in Patagonia, where they are said to have been numerous. Though these
last are slightly different, they are evidently referable to the sam e species ; they
also vary a little from each other. T heir peculiarities are as under :
T he largest measures 2 inches 8 lines in length, and has the following fin-
ray formula :
D . 12; A, 16 ; C. 16, & c.; P . 14 ; V. 7.
T he next in size is 2 inches 6 lines, w ith the fin-ray formula thus :
D . 1 1 ; A, 16; C. 16, &c. ; P . 13; V. 7.
T hese specim ens agree in being both slenderer than the one from T ierra del
Fnego. T he depth is eight and a half, if not nine times in the entire length : the
head rath er more than one-sixth of the same. T he colours are sim ilar except
th at the spots are not quite so numerous, and of a more regular form, seldom
running together to form bars.
It is to these specim ens th at Mr. D arw in's notes refer, respecting the colours
of this species in the recent state. As follow s: “ Pale greenish brown, with small
irregular transverse bars of black ; belly snow w hite.”—D.
T he third of the Patagonian specim ens is 2 in. 2 lin. long.
D . 10 ; A. 15 ; C. 16, & c.; P . 14; V. 7.
T he fourth is of the sam e length.
D , 11 ; A. 15 ; C. 16, & c; P . 13; V. 7.
Fin-ray formula-
T hese last two specim ens are exactly sim ilar to each other in colours, but
differ from the former two in being almost imm aculate, having only a few spots
on the upper part of the back. T his brings them very close to the following
species, from which they are scarcely to be distinguished, except by their sm aller
eyes. I t should be observed further, th a t the fleshy part of the tail in these
specim ens has the upper and under edges fringed with the short accessory rays
of the caudal, a character which is not so obvious in any of the others.
2 , M e s it e s a lp in u s . Jen.
M . viridescenti-fuscm, dorso saturatiore ; hoc, et lateribus, et pinnis, nigro levissimi
irroratis, immaculatis ; ventre niveo ; oculis majusculis.
D . 10; A. 16; C. 16, & c.; P . 13; V. 7.
L o n g . u n c . 2. lin . 5.
F o rm .—Very little difference in form between this and the last species. Tbe eyes, however, are
decidedly larger, measnring in diameter one-third the length of tho head. 'The head itself
also appears somewhat longer, being nearly one-fifth of the entire length. T he anterior teeth
on the tongue do not seem much larger than the others. Fins similar.
C o l o u r .— (/n spirits). Greenish brown, deepening in tin t at the top of the back. Back, sides,
and fins, immaculate, but thickly powdered with minute dark specks, scarcely visible except
under a lens. These specks give the fins a more dusky appearance than they possess in the
last species. The belly appears to have been white.
A second specimen, does not differ from the above in any respect, except in being rather
smaller, and scarcely more than two inches in length.
H abitat, T ierra del Fuego.
T his species was taken by Mr. Darwin in alpine fresh-w ater lakes in H ardy
Peninsula, T ierra del Fuego. I have no hesitation in considering it distinct from
the last, as there are two specimens exactly similar, both shewing a larger eye,
and an entire absence of all approach to sp o ts; while the whole surface of the
back and sides is thickly irrorated with dark specks, a character whicli does not
appear in the plain varieties of the M. maculatus.
3. M e s it e s a t t e n u a t u s . Jen.
P l a t e X X II. fig. 5.
3 i. viridescent:-fuscus, venire vix pallidiore; dorso, et lateribus, pinnarumque radiis,
sparsim nigro levissimd irroratis, immacxdatis: corpore pragx-acili, antich attenuato ;
capite et oculis minoribus.
D . 11 ; A. 17; C. 16, &c. ; P . 12 ; V. 7.
L o n g . unc. 2. lin. 0.
F o rm .— R ather more slender than either of the last two species, the body more attenuated anteriorly
; the head also smaller, though scarcely shorter. M outh and eyes both sm aller; the
diameter of the latter not more than one-fourth of the length of the head. Teeth also rather
more minute as well as more numerous. Tho fins arc similar, except that the ventrals appear
to stand rather more forward, being attached exactly in tbe middle of the entire length, excluding
caud al: the distance from their insertion to the commencement of the anal is more
than twice their own length. T he outer rays of the caudal are worn, but there was probably
a shallow notch when e n tire : the short accessory rays are very numerous, and form a very
distinct fringe along the upper and lower edges of the fleshy part of the tail.
IBM B