304 Professor MacGillivray on the Cirripedia. 
panded and emarginate, the apex obtuse, extending only to a third of 
the length of the upper lateral plate. 
The epidermis on the margins of the calcareous plates is generally 
bright scarlet, between the plates dusky, sometimes pale, rarely scarlet. 
The peduncle short, about the length of the tegmen, rugoso-granulate, 
with very small, unequal, roundish, flattened tubercles, greyish or 
brownish-black, at the base often pale grey, at the top reddish; its in- 
ternal or dermal tube greyish-brown. 
Very young individuals, two-twelfths of an inch in length, and others 
up to half an inch, have the peduncle and membranes generally dusky, 
being only of a lighter tint than in the adult. 
Very considerable variations occur in the outline of the tegmen; in 
the form of the plates, and especially of the upper, as well as the dorsal ; 
in the convexity of the lower, and the prominence of its umbonal angle; 
and in the lustre and distinctness of the striz; but, in all the varieties, 
there is no possibility of mistaking the species, or of not seeing that 
it is very distinct from any other. 
Generally semicordate, the teginen never varies in the convexity of its 
basal line; but the ventral line may be quite straight, generally sinuate, 
more or less recurved at the end, sometimes remarkably so, the apex 
generally obtuse, sometimes obliquely truncate, rarely narrowly and 
directly truncate. The lower plate has the ridge from the umbo to the 
point obsolete, slight, scarcely ever very prominent, always very close 
to the margin, and nearly parallel to it; its sutural margin almost 
always convex, rarely straight. In the upper plate, the umbonal angle 
is sometimes obsolete, sometimes distinct. The dorsal piece may be 
broader or narrower, always convex, and sulcate, generally with a keel 
more prominent toward the base. ‘The strive sometimes pretty distinct, 
the lustre glossy, seldom iridescent, often dull. 
The bluish tint of the plates is entirely owing to the dark pigment and 
mantle ; for when they are removed the colour is pure white, with a faint 
tinge of reddish-purple. 
It is needless to compare this species with Lepas anatifera, or any 
other known to me, as it is readily distinguishable. Its semicordate, 
subrecurvate form, the greater convexity of its basal plates, the greater 
breadth and less elongation of its dorsal piece, and other characters, 
might be noticed. The cirri are much longer, and have more joints; and 
their colour, as well as that of the body, is much darker. 
Lepas tegmine ovato-oblongo, subincurvato, basi convexo, rotundato, 
apice obtuso, cirrisultimis articulis 45 nigrescentibus, &c. 
Lepas tegmine ovato, basi compresso, subrecto, apice oblique truncato, 
cirris articulis 35, flavicantibus, &c. 
The following are the dimensions of several individuals :— 
Length, 1 4 ES dees ie ey PeAg 1 4 
Depth, siameanie OG 0 8 0 9 O 8 0 7 0 93- 
Waidth,. ..°. 0 4 0 4 0 44 #O 4 0 3 O 4% 
Peduncle, 0 10 0 10 0 8 0 6 OS 0 9 
This species was more abundant than the others, and its peculiar form 
struck me the moment I saw it, as being very different from that of any 
other species known to me. As to its specific rank there can be no 
doubt; and if it has already been described, no harm can ensue from 
my having given so long an account of it. The naming of a new species 
