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 the}^ 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 XXVII. 



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 



