[5 b], [Chthamalus Hembeli], younger shell;
C, carino-lateral compartment;
a′, ala; d, radius;
E, carina; a′, the two alæ.
[5 c], [Chthamalus Hembeli], scutum, external view of;
[5 d], tergum, external view of;
e, two of the crests, to which the tergal depressor muscles are attached, much
enlarged and viewed from vertically beneath, showing the lateral denticuli or sub-crests.
Fig. [1 a], [Chthamalus intertextus], shell;
[1 b], scutum and tergum, calcified together, with the suture obliterated in the upper part,
internal view of.
[2 a], [Chthamalus scabrosus], shell;
[2 b], scutum, internal view of;
[2 c], tergum, internal view,
p, plate forming one side of the cavity in which the depressor muscle is attached;
[2 d], tergum, as seen from almost vertically beneath;
p, pit for the depressor muscle;
q, special pit for the lateral, properly scutal depressor muscle;
r, articular furrow.
[3 a], [Chamæsipho columna], shell;
A, rostrum;
B, lateral compartment, probably formed by fusion of the rostro-lateral
and lateral compartments;
E, carina;
[3 b], [3 c] scutum and tergum, internal views of.
[4 a], [Chamæsipho scutelliformis], shell much enlarged, seen from above;
A, rostrum, separated by imperfect sutures from the
(B) lateral compartments, which are formed probably
by the fusion of the rostro-lateral and lateral compartments;
E, carina;
B stands opposite one of the inward
folds of the wall, leading into one of the tubular apertures,
which runs (generally with an irregular spiral curve)
through the whole thickness of the shell down to the surface
of attachment. The carina has two of these apertures.
[5 a], [Pachylasma giganteum];
[5 b], rostrum of an extremely young specimen, much enlarged, showing its
compounded nature, viz., of a true rostrum and rostro-lateral compartments;
[5 c], scutum and tergum, external views of;
[5 d], scutum and tergum, internal views of.
Fig. [1 a], [Pachylasma aurantiacum], shell, lateral view;
A, rostrum, separated only by the finest suture from
B, the rostro-lateral compartment, which latter has a mere rim-like
radius on the side facing the lateral (C) compartment.
The latter (C) has a great ala, and is separated from the
(D) carino-lateral compartment, by the finest suture;
D has a rim-like radius;
E, carina, with very large alæ (a).
[1 b], [Pachylasma aurantiacum], inside view of about half the shell,
showing the compound rostrum, consisting of the true
rostrum (A) and the two rostro-lateral (B, B) compartments;
of the latter, that to the left has a shoulder, receiving the
ala of the lateral compartment which has been removed;
the ala of the lateral compartment extends, in the upper
part, over the whole width of the rostro-lateral compartment,
as may be seen on the right-hand, B; C, lateral
compartment;
D, carino-lateral compartment, with a
shoulder (b) to receive the ala of the carina, which has been removed.
[4 b],””external view of one of the scales or valves, from the second whorl,
counting from the inside.
[4 c],””outline of the basal edges of all the
valves of a shell;
A, rostrum;
B, rostro-lateral;
C, lateral;
D, carino-lateral compartments;
E, carina.
[4 d],””external view of a portion of the shell of a much corroded and worn
down specimen, serving almost as a transverse section;
C, lateral compartment,
D, carino-lateral compartment.