SERPULAR1A TUBULARIA. 163 



is usually opake and milky. In some species it is trans- 

 parent and brilliant as glass ; in some it is round, in 

 others sharply angular ; in some perfectly smooth, in 

 others transversely wrinkled. Some species constantly 

 coil up their tubes in a nearly-regular, spiral manner, 

 others twist them into every variety of shape. In some 

 the tube is prosti'ate, in others erect ; and in some it is 

 prostrate during its early growth, and afterwards, when 

 the animal has attained a mature size, rises upward, 

 free and erect. Some kinds live in society, others are 

 solitary. One of the largest of our British kinds, S. 

 tubularia, represented in our figure, is very commonly 

 brought up in the dredge, attached to old dead shells, 

 &c., on scallop-banks. It generally is solitary, one 

 Serpula occupying a shell to itself, over whose surface 

 it first winds its way with gradually-widening tube, 

 until, having acquired nearly its full diameter, it rises 

 from the shell with graceful bend, and prolongs its tube 

 in an erect position to the length of three or four 

 inches. The tube is about the thickness of a quill, 

 of a dull white colour, cylindrical, and marked with 

 a few transverse wrinkles at short intervals. Within 

 this tube the animal can wholly retreat, closing the 

 aperture by means of a shelly plate affixed to a fleshy 

 horn, which rises at one side of the mouth. When the 

 animal displays itself, as it opens while seeking for 

 prey, its head, surrounded by the richly-coloured collar 

 of gills, composed of numerous slender pieces, pecti- 

 nated on their inner faces and spreading like a starry- 

 flower, is protruded for some distance from the tube ; 

 and here it waits, ready to seize on any small animal 



