_Genera_--PACHYLASMA, OCTOMERIS, AND CATOPHRAGMUS.
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.
1 _c_, 1 _d_, Pachylasma aurantiacum, scutum and tergum,
external views of.
2 _a_, Octomeris angulosa, shell seen from above; 2 _b_,
scutum and tergum, internal views of.
3 _a_, Octomeris brunnea, shell seen from above; 3 _b_,
scutum and tergum, external views of.
4 _a_, Catophragmus polymerus, shell seen from above.
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.
4 _e_, " " scutum and tergum, internal views
of.