Note 7 — Chapter IX · DEVELOPMENTAL HISTORY OF ENTOMOSTRACA, CIRRIPEDES, AND RHIZOCEPHALA.
W. S. (William Sweetland) Dallas translation
Darwin describes as “acoustic orifices” small apertures in the shell of the pupæ of the Cirripedia, which, frequently surrounded by a border, are situated, in Lepas pectinata, upon short, horn-like processes. I feel scarcely any hesitation in regarding the apertures as those of the “shell-glands,” and the horn-like processes as remains of the frontal horns.