127 



Figure. 



Triphoris grandis. PL 12. Pig. 55. Shell magnified to twice the natural 

 size, showing its reversed growth, rounded aperture, and recurved 

 tubular canal. 



Family 6. PARASITICA. 



Animal ; marine, parasitic, living imbedded in the soft parts of 

 the Star Fish, and producing a thin hyaline turbinated shell. 



The family Parasitica is one which I had occasion to propose about 

 five years since, in my ' Conchologia Systematica/ for the introduction 

 of a genus, well known to English conchologists but ill-understood on 

 the continent, named Stilifer, representing a small pectinibranchiate mol- 

 lusk, so peculiar in its habits that it could not be referred with propriety 

 to any of the existing groups. Mr. Gray includes the genus in his familv 

 Natieidce, but as the shell is very different in its structure and turbinate 

 growth from any of the Natica tribe, and the character and affinities of the 

 animal do not appear to be fully comprehended, I shall not at present 

 venture upon any removal. 



Of the species known, all appear to belong to one genus though mate- 

 rially differing in the form of the shell, and they are remarkably distin- 

 guished by their parasitic habit of growth, living imbedded in the soft 

 parts of the Star Pish, from the juices of which it is believed they obtain 

 nourishment. 



Genus 1. STILIFER, Broderip. 



Animal; disk narrow, slender, very much produced beyond the 

 head in front and but little extended behind ; head small, 

 rounded, with two elongate subulate tentacles having the eyes 

 on the outer side of their base ; mantle wholly contained ivithin 

 the shell. 



Shell; extremely thin, hyaline, transparent, either globose con- 

 sisting of few whorls, or elongated composed of many ; apex 

 elevated, obtuse, and mostly bent or rudely twisted; aperture 

 entire below, slightly sinuated at the upper part with the lip 

 extremely thin and delicate. 



The interesting little parasite which forms the subject of this genus was 



