192 TEREBELLA. 
now under discussion, which are far removed from them by modern 
systematic arrangements. 
The figure and the habits of the Terebella figulus, which may be 
most appropriately explained the potter, from its operations, as its chosen 
materials resemble the preceding species under a few modifications. Like 
the Sand Mason it is an architect, equally industrious, though less skil- 
ful. Where circumstances allow, it selects soft mud or clay exclusively 
for the materials of its dwelling, which also is fashioned of a tubular 
form, heavy, thick, and clumsy, instead of the comparatively light, thin, 
and fragile sandy edifice above described. It is smaller, and of more 
irregular shape. 
The dimensions of this animal are generally much inferior to those 
of the former, but the product of its labours, if estimated by quantity, 
much surpasses the proportion, and is more speedily executed. 
Were such delicate and defenceless beings liable to protracted expo- 
sure, they would be quickly sacrificed by numberless rapacious enemies 
ever in quest of prey, thence do they seem to know instinctively how 
they should be guarded from danger, or how to secure the readiest re- 
treat. 
For the most part the individuals of this species establish themselves 
in empty shells in deep water. But the finest specimen of all, I obtained 
casually on breaking up the shelving floor of a recess left in a shallow 
pool by the tide, wherein it seemed to have a permanent dwelling of the 
neighbouring softer substances.—Plate XX VIT. 
Length of the body about three inches and a half; thickness of the 
anterior part about three lines. Twenty-four pencils, each consisting of 
several bristles, issue from each side of the body, which afterwards be- 
come serrated down to the lower extremity. But many smaller specimens 
have only twelve pencils on each side, perhaps indicating another species 
or variety, for distinctions are not so readily seized by the observer, as 
in animals of definite parts in number and dimensions. Twelve elliptical 
prominences, with the rudiments of one or two cross the belly ; a 
deep groove from the lowest runs farther down. The skin of the first 
segment of the body advances in a kind of scoop, with the broader edge 
