[4], Section, in a vertical plane, through the skin of a whale, on which a [Coronula diadema] had been attached, but has been wholly removed: the two curved, horn-like projections occupied two of the eighteen cavities on the under side of the shell, formed by the folded walls: the blacker part is the epidermis; the lighter part is the yellowish fibrous tissue of the skin under the epidermis.
[6], [Coronula barbara], internal view of the basal margin and inside of one of the compartments, exhibiting the circumferential transversely looped ends of the folds of the wall, with the inner surface transversely wrinkled.
[7-9], diagrams, showing how one of the circumferential transverse loops of the wall becomes divided into two transverse loops, thus giving rise to another fold in the wall.
[10], diagrams, showing how the wall of the young shell in [Coronula], from being (a) simply sinuous, becomes deeply folded (b); the folds lastly (c) expanding transversely at their ends, thus giving rise to the circumferential transverse loops, as in fig. 7.
a, sheath, marked transversely in the upper part by the attachment
of the opercular membrane.
b, furrow on each side of (a), receiving the edges of the thick
alæ of the adjoining lateral compartments.
c′′, special plate, on which the alæ on their outer sides rest.
d, radius, on the edge it may be just seen to consist of an outer
layer (the normal radius), and a much thicker inner part
(the pseudo or complementary radius) formed of oblique
denticulated septa.
e e′ e′′, basal edge of wall, which from its commencement at
e, or e′′ can be followed, folding up to near the basal edge
of the sheath, to its termination at e′′ or e.
f, serrated lines of junction between the folds of the wall.
[2], Lateral compartment of [C. diadema], seen laterally, on a smaller
scale than last fig., but taken from the same shell;
letters of reference the same: this figure, if the ala a′ were
removed, would do for a lateral view of the rostrum, or fig. 1.
a, sheath, much foreshortened.
a′, ala (therefore also part of sheath), and the edge of which
fits into b of fig. 1.
b, furrow receiving edge of ala of the adjoining carino-lateral
compartment.
c′′, special plate, seen edgeways.
d, radius, the division into two parts, viz., the thin outer normal
radius, and the under pseudo or complementary radius
here shown (rather exaggerated) plainer than in fig. 1.
e, basal edge of wall; to the right hand the three folds at their
inner ends are seen obliquely, one behind the other:
these are seen directly in front in fig. 1.
[3], lateral compartment of [C. balænaris], seen laterally; letters of
reference the same as in last fig., but c′′ not introduced for
this plate is barely developed, and only in the lower part,
and is attached to the radius: g g points where fresh folds
have been formed in the walls along the lines of suture,
as may be seen in the outline of the wall in fig. 5.
[4], lateral compartment of [C. reginæ], seen laterally; letters of
reference the same as in the last two figures.
[5], [Coronula balænaris], outline of the basal margin of the folded walls:
s, s, the six sutures. The wall can be continuously
followed from one end of a suture to the next suture.
[6], [Coronula diadema]; small portion of the external surface of the
wall, close to the basal edge, highly magnified;
a, outer lamina, not extending down to the basal edge;
b, inner lamina;
c, projecting longitudinal septa.
[7], [Coronula diadema]; transverse section through the upper part
of the shell, showing the rostrum and the two adjoining
lateral compartments (and the alæ of the carino-lateral
compartments), all supposed to be a little separated from
each other, so that the sutures, s s, are shown by white lines.
A A A, rostrum.
C C, lateral compartments.
D D, carino-lateral compartments, of which only the alæ (a′) are shown.
Of the letters in italics, those which occur in figs. 1, 2, 3, 4, 5, refer all to the same parts, viz.:—
a, sheath, continuous with (a′) the alæ, where such occur.
c′′, special plate on which the alæ rest.
d, radius, divided into a thin outer normal radius, and the inner
complementary portion, the latter shaded by convex lines of growth.
d′ is a special tube (seen only as a black dot) for a thread of corium.
e, folded walls.
f, junction of the folded walls (see f, in fig. 1) leading into the cavities (f′)
open beneath, and filled up by the epidermis (see Pl. [15], fig. 4) of the whale.
h, inside of the transverse loops of wall, occupied by corium:
in the enlarged section of a loop, in [C. balænaris], in Pl. [15],
fig. 2 a, the opposed sides are seen to be connected by
shelly longitudinal plates.
Fig. [1 a], [Platylepas bissexlobata], shell of, viewed from the under side;
A, rostrum;
B, lateral compartment;
C, carino-lateral compartment;
E, carina.
These letters are placed opposite the inward folds of each compartment forming the midribs.
[1 c],””scutum and tergum, viewed externally and separated.
[1 d],””lateral compartment, viewed from the inside, showing the inward folded wall or midrib;
a′, ala; d, radius.
[2 a], [Platylepas decorata], shell, viewed externally;
A, rostrum;
B, lateral compartment;
C, carino-lateral compartment;
E, carina.
These letters are placed opposite the inward folds of each compartment.
[2 b],””minute portion of external surface of wall, magnified.
[3 b], [Tubicinella trachealis], carino-lateral compartment of a young specimen, natural size;
e, broken summit of wall;
d, radius: the dotted lines, connecting the two figures, show the size
and form which this compartment would have attained, if it
could have grown without the summit constantly breaking away.
[3 c], [Tubicinella trachealis], scutum and tergum viewed from within, and connected by layers of thickened membrane;
the scutum is to the left-hand.
[4 a], [Xenobalanus globicipitis], enlarged;
b, skin of the porpoise, with the shell imbedded;
at c the lower end of the prosoma of the included animal’s body is supposed to be seen through.
[4 b], [Xenobalanus globicipitis], shell greatly enlarged, seen from above, with the basal membrane at the bottom; the
peduncle-formed body having been removed.
A, rostrum, on the inner side of this and the adjoining compartments,
the transversely ribbed sheath can be seen.
B, lateral compartment.
C, carino-lateral compartment.
E, carina; these compartments are separated by the sutures s s,
which run from the top of the shell to the bottom, along the
ends of the six rays formed by the adjoining portions of
the inwardly folded compartments.
a, alæ, of rectangular shape.
d, pseudo, or complimentary radii.
[4 c], [Xenobalanus globicipitis], small portion of external surface
of wall of shell, showing the external lamina, a a, which
consists only of narrow ledges (expanding and contracting)
on each side of the longitudinal septa, c; b, the internal
lamina.