552 



The animals of S. Chryfodon, conchilega, and<:2>r(2" 

 ^(^,, approach each other fo nearly, about the hind, or 

 anterior part, that aftual comparifon is abfolutely re- 

 quifite to dillinguifli them ; the bodies, however, fome- 

 what differ; but the number of joints is not wholly to 

 be depended on in fome fpccies ; the cafes or tubes, as 

 well as the habits of the animals, are eflential auxiliaries 

 in this clafs of animated nature. 



8. "^ 



Arenaria. S. with an extremely fragile, cylindric tube, com- 



pofed of pure fand, (lightly cemented together without 

 any internal membrane, like S. granulata, but is never 

 fo large, and is equal in fize at both ends. 



This is very common on the DorfetJJiire coaft, efpeci- 

 ally at Weymouth and Portland; and are driven up in 

 fuch abundance at Studland, that the beach is cover-ed 

 v/ith them. Thefe are ufually from one to two inches in 

 length, and about the fize of a raven's quill ; but are 

 probably only fragments, or that part of the tube the 

 animal forms above the fand, which is continually de- 

 llroyed by every little increafed agitation of the fea, 

 and as frequently replaced. 



The animal unknown. 



SuLCYLiNDRicA S, with.a long, fub-cylindric, flender, fragile tube, 

 compofed of fine fand, and minute bits of broken fliells, 



cement- 



