328 Mr. Jeffreys on Stilifer, 
mide and Cerithiopside; Clark in Pyramidellide, between Aclis 
and Scalaria; and Gray also in the same family, between his 
genus Hyala (Rissoa vitrea) and Entoconcha. Iam inclined to 
agree with the Messrs. Adams in making Séilifer the type of a 
separate family; but it is much more difficult to say to what 
other families it has the nearest affinity. Pyramidellide, as re- 
presented in our seas by Odostomia, ought not to be far sepa- 
rated from it; and Janthinide have similar relations to it in 
respect of the nucleus or apex of the shell. Homalogyra has 
sessile eyes placed on the neck, asin Séeifer, but has no tenta- 
cles ; and it is also finely ciliated all over. 
The presence or absence of an operculum is evidently not a 
character of sufficient value to distinguish one family, or even 
one genus, from another, seeing that some species of the same 
genus (e.g. Mangelia) possess an operculum, while their con- 
geners (although closely allied in all other respects) have none. 
The styliform character of the spire in this genus, although 
remarkable, is not peculiar to it, or to Odostomia, Turbonilla 
(or Chemnitzia), Eulimella, or Ianthina. Melampus bulleoides has 
the apical whorls formed in the same mamillated fashion ; and 
in several genera of Bullide the shell exhibits the same feature. 
These, however, may be regarded as cases of analogy rather than 
of affinity. The nucleus of the spire, or first-formed whorls, in 
many univalves ceases to be occupied by the animal after it has 
attained a certain growth, being too small for its requirements— 
like a householder, who usually moves, once at least during his 
life, into a tenement larger than the one he at first inhabited. 
In the case of the Mollusca above referred to, the original and now 
useless tenement remains fixed to the new one; but in Bulimus 
decollatus, some species of Clausilia, andin Truncatella truncatula 
the topmost story is knocked off and replaced by a partition 
wall. Caecum glabrum and C. trachea even undergo partial meta- 
morphoses, the shell of each having at first a regular spire, and, 
when this is lost, becoming a slightly curved cylinder. The 
genera Leptoconchus of Riippell and Campulotus of Guettard 
(Magilus, Montfort) also appear to be related to Stilfer in their 
quasiparasitic habits. The first-named genus is destitute of 
an operculum, except in its younger state; the other has an 
operculum at all ages (Deshayes, Moll. de Pile de Réunion). 
The conjecture of the late Professor d’Orbigny that Stilifer 
ought to merge in Eulima, and that the latter may be also para- 
sitic, has no foundation. It is true that species of Hulima have 
been found in the stomachs of Holothuria ; and the “ trepang,” 
or dried béche de mer, of which the Japanese are so fond, fre- 
quently contains these shells. But this is not a case of parasitism : 
the Eulima feeds the Holothuria, instead of feeding upon it. 
