192 PECTINIBRANCHIATA.—PYRAMIDELLADA. 
the last whorl of the shell, but Mr. Adams from 
observation on the living animal, informs us that it 
is entirely enclosed and covered by the thin shell, 
while the foot is narrow, slender, and very much 
produced beyond the head in front. 
The habits of this teresting mollusk are most 
singular, for it is found to live parasitically upon 
the animals of the class Hchinodermata (Star-fishes 
and Sea-Urchins). Three species are known, one 
of which (Stylifer Turton?) is a rare inhabitant of 
the British seas. Dr. Turton, how- 
ever, its discoverer, found no fewer 
than a dozen attached to the spines 
of Hchinus sphera, dredged in 'Tor- 
bay. It has since been found in 
several localities, as on the coasts 
of Northumberland, Durham, and 
Cork, always under similar circum- 
stances. Mr. Alder states, that it occurs on young 
Sea-Urchins. 
A fine species was discovered in the Indian 
Archipelago by Mr. Hugh Cuming, and named 
S. astericola. He found this elegant parasite 
burrowing in different parts of the oral dise of 
Asterias solaris. It was almost hidden from sight, 
so deeply does the animal penetrate into the sub- 
stance of the star-fish, in which it makes itself a 
comfortable cyst (or cell) for itself, and wherein it 
most probably turns by aid of its rudimentary foot. 
All the specimens infested with these testaceous 
mollusks appeared to be in the best health, though 
there is reason to believe that they feed upon the 
juices of the Star-fish. Mr. Broderip observes that 
Stylifer (with that instinct of self-preservation which 
is imparted to all parasites whose existence depends 
STYLIFER. 
