404 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The plates are small and well removed from one another. Each scutum (fig. 2) is composed of 
two segments united at the umbone by an uncalcified flexible portion; the occludent segment extends 
parallel and close to the occludent margin of the capitulum; is widest in the middle, where it is about 
half as wide as the lower part of the tergum; is narrower near the umbone, and at its upper end is 
always more or less pointed. The point is directed toward the notch in the tergum and reaches to or 
a little beyond the lower edge of that plate. Between this segment and the basal segment, which lies 
parallel to the base of the capitulum, is an angle varying from 70° to nearly 90°. The basal part is 
narrower and about five-sixths as long as occludent portion, is of a more uniform width, and, though 
often ending rather bluntly, is usually pointed. It may not reach quite to the points of the prongs 
of carina, or may overlap them as much as two-thirds their length. One scutum was found with a 
third narrower segment between the other two and directed toward the upper end of the carina. 
Each tergum bears a notch on the occludent margin (figs. 2, 4, and 5). If the notch is measured 
from its apex to the tip of the smaller, occludent portion of the plate, its depth is generally about 
one-sixth (though itmay be one-third) the length of the tergum or less. The lower end of the tergum 
is in width usually one-half (one-third to three-fourths) the length of the plate; generally it has a 
smooth outline, though sometimes a little jagged or with a notch. The carinal margin is usually slightly 
concave; this side, too, sometimes bears more or less of a notch. The upper end is blunt and rounded. 
Length of tergum two-thirds that of scutum, or one-third that of capitulum. That the two terga of 
the same individual are not necessarily just alike is shown by figs. 4 and 5; in each figure the dotted 
line represents the tergum of one side, the continuous line that of the other side, of one barnacle. 
Fig. 3. — Diagrammatic Fig. 4. — Outlines of the two terga Fig. 5. — Same of another 
sketch of valves. of an individual, x 30. individual, x 30. 
Fig. 6.— Lower part of a 
carina. x 30. 
The carina (figs. 2 and 6), terminating downward 'in a fork, is much widened at the base of the 
widely separated and pointed prongs. Above the fork the carina is of very nearly uniform width. 
It ends bluntly, reaching to or barely beyond the lower edges of the terga; in a few cases it extends 
up between the terga as much as halfway. Within it is convex. 
The mouth-parts are well developed. On the labrurn are two rows of short teeth, set closely 
together in the middle; the palpi are about equal in size to the first maxillte, and are clothed on and 
near the inner edge with bristles. The mandibles (fig. 7) have four teeth — the lower angle appears 
as a fifth tooth — the second being farther removed from the first than from the fourth; the lower 
three teeth are a little less sharp than the first; on the inferior angle are two or three very short teeth 
and as many stout spines; below it are a number of closely crowded slender spines; the mandible is 
hairy near the end and bears little tufts of hairs on its outer margin. The second maxilla has four 
spines above the notch (one is small), two slender spines in the notch, and nine or ten below (fig. 8). 
The cirri of the first pair are removed from those of the second pair and are about half as long. 
Their rami are equal in length and are thickly clothed with spines. The rami of the second cirrus 
are of equal thickness and little shorter than those of the sixth. The caudal appendages, which are 
nearly as long as the pedicels of the sixth cirrus, are narrow and of very nearly uniform width 
throughout. They taper a very little at the end where is borne a tuft of 15 or 20 bristles, the longest 
of which are a little longer than the appendages. Sometimes other spines are found near the end. 
As seems to be the case in most species of the genus, the penis is very large, reaching in D. 
mulleri to or beyond the second cirrus. It tapers to a point and has a tuft of short bristles on the 
end. On each side are scattered bristles in three rows. 
