A Monograph on the Sub-class Cirripedia · Charles Darwin
PLATE 20.
_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.
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