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Genus STYLIFER, Broderip, 1832. 



Imperforate, hyaline, thin, ovoid or elongated, smooth, pol- 

 ished ; whorls numerous, apex very sharp, sometimes bent, 

 nucleus sinistral, last whorl globular ; aperture suboval, inner 

 lip smooth, arcuated, outer lip slightly sinuous, thin, simple. No 

 operculum. 



Body ciliated ; tentacles slender, subulate, with eyes sessile at 

 their outer bases ; mantle reflected upon and more or less sur- 

 rounding the shell, forming a siphonal lobe on the right side ; 

 foot linguiform, narrow, tubular in front, where it extends much 

 beyond the head, attenuated behind, with a median groove below; 

 verge sharp, elongated, resembling a tentacle. 



About twenty species are known from warm seas. 



Stylina, Fleming, 1828 (Gray), is a synonym. 



Stylifer is commensal or parasitic in its habits, occurring on 

 Echinoderms ; some are found in the teguments of Asteriae, 

 others on the upper face of the shells of Echini, between the 

 spines, and generally near the anal opening ; S. Orbignyanus 

 lodges itself in a spine of Cidaris, which becomes deformed in 

 growth, forming an interior cell containing a pair of Stylifers 

 and some young ones, the cell having a small mouth on either 

 side ; other species are obtained from Holothurians, Comatulse, 

 etc. 



The species mentioned above, inhabiting the spines of Cidaris, 

 appears to be viviparous, but S. Turtoni, on the contrary, is 

 oviparous. Those which live upon the external surface of their 

 host are probably commensal rather than truly parasitic. 



How does the S. Orbignyanus obtain nourishment ? 



Subgenus CYTHNIA, Carpenter, 1864. 



Imbedded in star fishes like Stylifer, from which it is distin- 

 guished by its normal nuclear whorls, and thin concentric oper- 

 culum. W. Coast of N. America. 



Subgenus PLICIFER, H. Adams, 1868. 



Imperforate, ovately subulate, not shining; spire styliform, 

 nucleus sinistral, columella plicate ; lip floxuous, sinuate behind, 

 aperture entire in front. Found on coral, at Ceylon ; the shell 

 resembles Leptoconchus in texture. 



