SHELLED SABELLA. 293 



the other day ; which is ever on the watch to insert its 

 snaky head within the unprotected tube, and to tear 

 away with merciless clutch the beauteous gill-tufts. 



One species of this genus 1 can by the cursory ob- 

 server be distinguished from the Serpulae, only by this 

 absence of the antennal stopper. For it dwells in a 

 shelly tube, essentially resembling those which we have 

 just been examining. It has peculiarities of detail, 

 however. It is never found associated with numbers 

 of its fellows in agglutinated groups, but always, so far 

 as my experience goes, singly. It is more common on 

 shells than on stones, generally attached to the old 

 valve of some cockle or scallop. It is straight or 

 nearly so, never at least contorted. Attached only for 

 a very short portion of its smaller end, perhaps for an 

 inch or so, for which it creeps along the surface, it then 

 rises into a more or less erect position, extending some- 

 times to a height of seven or eight inches perfectly 

 free. The tube is of about the same diameter as that of 

 the Serpula, but is slighter in structure, or perhaps it 

 appears so, because it is destitute of those expansions 

 which here and there in that species indicate the trum- 

 pet-lips of successive stages of development. The ex- 

 tremity of the tube here is simple, not expanding. 



1 Sdbella tubularia, represented as occupying the foreground and the 

 left-hand side of Plate xxxui. 



