SABELLA. 
115 
The Troclius conchyliophorus derives the same 
sort of protection from foreign substances, being 
covered however with entire stones and shells, in- 
stead of pulverised or broken pieces of them. In 
this case no one doubts the fact of its being a true 
Trochus, because the foundation of the aggregate 
is regularly spiral, and possesses the characteristic 
aperture. Why, then, should Sabella be expelled 
the order, as it often has been, because the sheath 
is not spiral, but straight and tubular? Some few 
species may have found admittance, which do not 
perhaps belong even to the class of Vermes, as the 
larvee of some insects are known to provide them- 
selves with a very similar receptacle to that of a 
real Sabella. There is one never-failing mark of 
genuineness in most perfect specimens of this ge- 
nus, — that of the end being, as it were, fringed, or 
produced into numerous ragged processes of the 
same nature with the shell. They are, however, 
so extremely friable, that perfect specimens are 
rather rare. The denomination of the tribe is 
taken from the principal constituent of their 
edifices, Sabulum, /h/e grave! or sand. 
