298 Professor MacGillivray on the Cirripedia. 
1. Lepas anatifera. Common Barnacle. 
Tegmen ovate, much compressed, obliquely truncate ; the lateral 
plates very thin, fragile, bluish-white, faintly iridescent, obsoletely 
rugoso-striate, with minute radiating striule ; the lower plate subovato- 
tetragonal, with the basal margin oblique and nearly straight, the poste- 
rior shorter and convex, the sutural straight or slightly concave, the apex 
rather obtuse; the upper plate oblong, obtuse at both ends, with the 
supra-umbonal side shorter than the anterior; the dorsal piece linear- 
oblong, obtusely carinate, sulcate, or striate ; the peduncle rugose, pale, 
the epidermic portion of the tegmen scarlet, orange, or yellow ; the cirri 
pale yellowish-grey. : 
The body of the animal is ovate, compressed, incurvate, very convex 
on the back, narrow behind ; anteriorly soft, with a membranous integu- 
ment, which becomes horny on the hind part, where it is marked be- 
neath with faint transverse depressions. The mouth prominent, with an 
induplicate or somewhat semilunar, bullate, rounded lip, with two thick, 
pointed palpi, which are adnate until toward the end, directed forwards 
or downwards, with the tip free and ciliate, and three pairs of incurvate, 
compressed maxillar appendages, lamelliform at the end. The first or 
outer pair, with the terminal lamina oblong, acute, with six external, 
marginal, long, acuminate teeth or serratures, of which the posterior are 
longest; the second with the lamina broad, with five short, broad teeth 
or lobes, and several bristles; the third, inner or medial, narrower, and 
ciliate. 
The first pair of feet, in‘the form of oblong, compressed bodies, are 
placed immediately above or behind the mouth, and bear each a pair of 
unequal, tapering, compressed, horny, articulated, incurvate cirri. The 
second pair are at some distance from the first, and the rest close toge- 
ther, subcylindrical, compressed, biarticulate ; their cirri longer. All 
the cirri are lobed and ciliate on the anterior or lower border, convex 
on the dorsal side, with a few very small bristles at each joint. The 
first pair of cirri with eighteen joints, the last with thirty-five joints and 
lobes, on each of which are generally about sixteen unequal ciliary bris- 
tles, in two divergent series. 
On each side, on a prominence at the base of the first foot, externally, 
is a long, subulate, soft, and flexible filament; and at some distance 
from it, on the side of the body, towards the back, is another, about half 
its length. 
The narrowed part of the body to which the five pairs of abdominal 
feet are laterally attached, is marked beneath with faint, irregular, 
transverse depressions between the feet, and thus perhaps subarticu- 
lated. It ends in a very long, slender, tapering flesh-coloured tube, 
usually curved inwards, but, when extended, exceeding the last cirri in 
length. At the base of this tube, on the dorsal aspect, is the anus, over 
which are two oblong, mobile, horny plates. 
The general colour of the body is pale purplish yellow, partly flesh- 
colour; the cirri yellowish-grey, or light horn-colour. 
A large round muscle, attached to the anterior part of the body, 
under the mouth, extends from one of the large calcareous plates of the 
tegmen to the other, like one of the adductor muscles of a bivalve shell. 
The body is also attached to the tegmen by muscular fasciculi, which 
expand beneath its integument over the viscera. 
The subsidiary dermal envelope or mantle is very thin, whitish, mar- 
gined at the aperture with an elastic scarlet or orange-coloured filament. 
Between it and the epidermic envelope or shell is a very delicate film of 
pale purplish-brown pigment, appearing like a film of China ink or neu- 
tral tint, divided into minute polygonal or circular fragments. 
