still more sedentary than the true Limpets, for there may be seen in certain individuals of the P. Hungaricus irregularities, proceeding from the body on which it has lived when young, continuing exactly the same to adult age; irregularities whose traces may be observed on the lines of growth, and which prove, in the opinion of M. Deshayes, that during its whole life the animal has never changed its place. But, probably, M. Deshayes was not aware of those interesting facts which have been observed in the habits of the true Limpets, already described in these pages; for, if a similar habit of roaming for food, and returning with precision to the exact spot which it has chosen as its home, be common to the Foolscaps also, it appears to me that the phenomena alluded to by the eminent French zoologist would be sufficiently accounted for without his hypothesis.
Family Dentaliadæ.
(Tusk-shells.)
On many a pebbly beach upon our coasts there is frequently found, among other shells washed up by the sea, one which bears the closest resemblance to an elephant's tusk in miniature. It is the representative of a family, comprising but a single genus, which is interesting because its characters, as well those of the shell as of the animal, manifest a decided approach to those of another great division of organized beings, the Articulata. Indeed it was formerly considered by the best zoologists to be a genus of Annelida, allied to those which form the shelly tubes so commonly seen on sub-
