Page:The Zoologist, 4th series, vol 4 (1900).djvu/348

318 sumes, refers merely to the appearance of the figures; for nothing appears to be known of the manner in which the threads are produced and attached. Adams's observations are referred to in nearly all the books, and figures based on his are found in Woodward and in Keferstein, that of the former having been repeated by Fischer and twice by Tryon. Mr. Tye, who refers to Woodward, has by mistake attributed the observations to Cerithidea decollata, an animal which does not appear to fix itself by threads, Dr. Gibbons having reported that large numbers seen by him on trunks of marsh trees in Natal were attached, not by threads, but by "a trifle of brittle mucus passing from the lip to the tree," a mode of attachment, as Dr. Gibbons says, resembling that of brackish water Littorinæ.

Planaxis has been listed among thread-making molluscs by Dr. Macdonald, but the writer does not know on what authority.

According to Mr. Harper Pease, two forms of Torinia (Hawaiian Islands) "suspend themselves by strong gelatinous threads, one of which will sustain the weight of several shells, and can be drawn out four or five inches"; the creatures are found almost invariably upon branched coral.

Among the crowd of little conical-shelled molluscs of the genus Odostomia, the use of a thread has been observed by Jeffreys in Odostomia warreni, whose foot is remarkable from being forked at the extremity like the tail of a Swallow. The