314 COMMON OBJECTS OF THE SHORE. 



grow, on any summer day, with the certainty of 

 finding it. When examined with a microscope, 

 the shell is seen to be shaped exactly like that of 

 the nautilus, and of a beautiful white silvery 

 nature; and when the little worm within puts 

 forth its delicate radiated branchial organs, like 

 so many exquisite feathers, we are ready to be- 

 lieve that scarcely any object in nature can be 

 more lovely or graceful. The shell is flat on one 

 side, and when severed from the sea-weed is seen 

 to have the flat side composed of a thin delicate 

 substance, like gauze-paper; for the sea- weed 

 forms a wall to the little dwelling, and, therefore, 

 the animal needs not to secrete a thicker material 

 at that part. 



Some of the marine annelides line the holes in 

 the sands in which they live with a calcareous 

 lining ; some make for themselves the most curious 

 and interesting little dwelling-places, composed 

 of broken shells firmly agglutinated together, a 

 curious mosaic work of little squares, and angles, 

 and circles, as the shape of their pieces may 

 chance to be. One little worm, unable to con- 

 struct a dwelling for itself, finds one exactly fitted 

 to it in the old shell of the mollusk, commonly 

 called Tooth-shell (Dentalium entalis), that little 

 shell so common on our coasts, shaped like a small 

 horn. This is taken possession of by the tooth* 

 shell Siphunculus (Siphunculus dentalii}, which, 

 having entered, seals up the entrance with a strong 

 and fixed plug of grains of sand cemented together, 

 leaving on one side a small circular hole, through 

 which it may protrude its long proboscis in search 

 of prey, yet small enough to prevent the entrance 

 of any enemy into its home. This worm is about 



