[1] In the Rules published by the British Association, the 12th edition, (1766,) is specified, but I am informed by Mr. Strickland that this is an error, and that the binomial method was followed in the 10th edition.
The Lepadidæ, or pedunculated Cirripedes, have been neglected under a systematic point of view, to a degree which I cannot quite understand: no doubt they are subject to considerable variation, and as long as the internal surfaces of the valves and all the organs of the animal’s body, are passed over as unimportant, there will occasionally be some difficulty in the identification of the several forms, and still more in settling the limits of the variability of the species. But I suspect the pedunculated Cirripedes have, in fact, been neglected owing to their close affinity, and the consequent necessity of their being included in the same Work with the Sessile Cirripedes; for these latter will ever present, I am fully convinced, insuperable difficulties in their identification by external characters alone.
I will here only further remark, that in the Introduction I have given my reasons for assigning distinct names to the several Valves, and to some parts of the included animal’s body; and that in the Introductory Remarks, under the general description of the Lepadidæ, I have given an abstract of my Anatomical Observations.
CORRIGENDA AND ADDENDA.
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[12], twenty lines from bottom, for “hinder pair of true thoracic limbs,” read “pair of true thoracic limbs.”
[42], 43. I should have added, that the number of the segments in the cirri increases with the age of the specimen; but that the relative numbers in the different cirri keep, as far as I have seen, nearly constant; hence the numbers are often given in the descriptions.
[99] et passim, for Pæcilasma, read Pœcilasma.
[156]. In a foot-note, I have alluded to a new genus of sessile Cirripedes, under the name of Siphonicella, I now find that this species has been called, by Professor Steenstrup, Xenobalanus globicipitis.