With respect to C. balænaris, I have seen only specimens, preserved on shrunk and twisted whale’s skin, with the underlying fibrous layer not preserved; but the cavities in the shell were filled by horns of epidermis, exactly as in C. diadema. There is, however, this difference in the attachment of the two species, that in C. balænaris, owing to its depressed form, the circumference of the shell indents the whale’s skin, not vertically downwards, as in C. diadema, but very obliquely outwards; and, consequently, buries itself much more completely, but less deeply, under a folded and apparently ruptured flap of the epidermis. In young specimens, of the size of a shilling, the entire shell, with the exception of the operculum, is thus covered up and protected whilst young and tender.

Geographical Distribution.—The genus is found wherever whales occur, that is, from the Arctic to the Equatorial regions, in both hemispheres. It is asserted that sometimes as many as a couple of hundred specimens will adhere to a single whale. Coronula barbara, a form closely allied to C. diadema, existed during the Red Crag period; and Bronn has described some fossil specimens from Italy.

Affinities.—In the wonderfully convoluted shell,—in the parietal tubes not being either filled up by calcareous layers or being crossed by calcareous septa,—in the outer lamina of the shell between the longitudinal septa near the basis being imperfect, Coronula differs from all the foregoing genera; in the two latter respects it agrees with the three following allied genera, viz., Platylepas, Tubicinella, and Xenobalanus. The equal size of all six compartments of the shell, has been observed in very few genera besides Coronula. In a new opercular membrane not being formed at each exuviation, and in two or three of these membranes being persistent, and in their being attached high up the sheath, this genus agrees with the three following genera alone. In the valves tending to be rudimentary, and in the protuberant lips of the sack-aperture, we have a close alliance with Xenobalanus. The muscles of the sack being spread out, and tending to lose their transversely striated character, are great peculiarities in Coronula, Tubicinella, and Xenobalanus. The simplicity of the cement-ducts is a remarkable character, observed in two of the following genera, but not in Tubicinella. The double branchiæ is a peculiarity common to all four genera. Neither the mouth nor cirri offer any new characters of much importance in Coronula or in the three allied genera: the lower teeth of the mandibles not being laterally double, but having small intermediate teeth, is the newest feature in the mouth.

---