328 Mr. JeflFreys on Stilifer, 



mida and Cerithiopsida ; Clark in Pyramidellida, between Aclis 

 and Scalaria ; and Gray also in the same family^ between his 

 genus Hyala [Rissoa vitrea) and Entoconcha. I am inclined to 

 agree with the Messrs, Adams in making Stilifer the type of a 

 separate family ; but it is much more difficult to say to what 

 other families it has the nearest affinity. PyramidellidcE, as re- 

 presented in our seas by Odostomia, ought not to be far sepa- 

 rated from it ; and lanthinidce have similar relations to it in 

 respect of the nucleus or apex of the shell. Homalogyra has 

 sessile eyes placed on the neck, as in Stilifer, 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 lanthina. Melampus bullceoides has 

 the apical whorls formed in the same maniillated fashion ; and 

 in several genera of Bullidce 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, and in Truncatella truncatula 

 the topmost story is knocked off and replaced by a partition 

 wall. Cacum 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 Stilifer 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 Vile de Reunion). 



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 Eulima have 

 been found in the stomachs of Holothurice ; and the " trepang," 

 or dried beche 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. 



