218 PECTINIBRANCHIATA.—DENTALIADA, 
or sandy mud, in from ten to one hundred fathoms;”’ 
but obtained most abundantly in from forty to 
seventy fathoms. 
Dr. Gray remarks that the apices of the British 
specimens often appear to be either broken off, or to 
have fallen off of themselves, like the tips of those 
shells called decollated, as some of the Helicide ; 
and he adds that when the tip is broken, the 
animal forms a slight tube within, which is more or 
less produced beyond the tip. Specimens in this 
condition have been described as distinct species. 
A parasitical worm, of the class Echinodermata, 
the Sipunculus Bernhardus, is frequently found 
inhabiting old and dead shells of the Dentalium, 
the mouth of which it closes, except a minute 
orifice, with a sort of mortar made with sand. 
This parasite has sometimes been mistaken for the 
original inhabitant of the shell. 
