RHIZOCHILUS. 135 



Genus RHIZOCHILUS, Steenstnip. 



Shell, when young, free, resembling Rapana ; when 

 adult, sometimes with more or less irregular, solid, shelly- 

 extensions of the outer and inner lips, which clasp the 

 axis of coral, or the surface of neighbouring shells, and at 

 length close the mouth, with the exception of the ante- 

 rior siphonal canal which is converted into a shelly tube. 



Ex. R. antipathicus, Steenstrup, pi. 14, fig. 5, 5, a. 



The remarkable peculiarity of the animal of Rhizochi- 

 lus, at least in the typical species, in becoming perma- 

 nently fixed, and closing the aperture of the shell, is very 

 anomalous. Like Pediculnria , it attaches itself to the 

 axis of coral ; it frequently, however, adheres to shells of 

 its own kind. Professor Steenstrup observed it embracing 

 the axis of AntipatJiefi ericoides, whence its specific name. 



Species of RhizocJdlus, 

 antipathicus, Steenst. 



Sub-gen. coKALLioPniLA, H. and A. Adams. 



Shell with the outer and inner lips irregular, moderate, not 

 produced into an extended process closing the aperture. 



clathratus, A. Adams. monodonta, Qicoy and Gaim. 



costularis, Blainv. neritoideus, Chem. 



D'Orbignyanus, Petit. osculans, C. B. Adams. 



foveolatus, C. B. Adams. pulchellus, A. Adams. 



fragiUs A. Adams. scala, A. Adams. 



galea, Chem. scalariformis, Lam. 



gibbosus, Reeve. squaniulosus, Eeeve. 



madreporinus, A. Adams. suturalis, A. Adams. 



