upon that of their nidus) appears, like the larvæ of the ichneumon tribes among insects, to avoid the vital parts; for in no instance did Mr. Cuming find it imbedded anywhere save in the rays, though some of the individuals had penetrated at their base, and very near the disc. When extracted, the older shells have the appearance of a milky-clouded glass bubble: the younger shells Mr. Broderip found of an unclouded transparency.
Though very limited in numbers, this family is interesting to the conchologist as containing some species of singular form and remarkable beauty, one of which was formerly valued so highly as to command enormous prices, and to have acquired the name of the Precious Wentletrap. "In this family a spiral shell with an entire aperture is combined with an animal whose head is not produced into a muzzle, but furnished with a retractile trunk. The sexes are distinctly separated. The eyes are immersed at the external bases of subulate (awl-shaped) tentacles." The dentition of the ribbon-like tongue is very peculiar; there is no central tooth differing from the rest, but all are alike, arranged in transverse rows, and forming simple claw-like hooks. The animals are probably predaceous like the Whelks, &c. Most of the species, which amount to nearly a hundred, inhabit the seas of warm climates, though a few are found on our own shores.