SCULPTUEED SHELLS. 169 



apparently by the pushing outwards and inflating of the 

 two extremities of the body. At this moment a white 

 line flies round the anterior end of the egg : it is a crack, 

 and the next instant the separated portion of the egg-shell 

 is pushed off", and the head protrudes, the cilia waving 

 nimbly in the water. A moment the new-bom young 

 sits in the shell as in a nest; but now it glides forth, 

 and we see that in every point of form and structure it 

 is the very counterpart of its parent, the shell, the foot, 

 all the internal viscera, being perfect and comme il faut. 



The shells in which these little creatures are enveloped 

 are models of symmetry and elegance, and display great 

 variety of form. Some of them are sculptured in cmious 

 and beautiful patterns, an elaboration which is truly sur- 

 prising when we think of the invisible minuteness of the 

 entire creature. One is clothed* with a shell of the 

 usual glassy mail, nearly circular in outline, very flat, 

 but a little arched on the back aspect, the chin hollowed 

 out in a semicircle, and the brow armed with two horns 

 curving downward ; the posterior extremity square, with 

 two lateral spines. The entire surface of this shell is 

 covered with minute elevated points, which extend even to 

 the horns and spines ; and besides these, the dorsal sur- 

 face is marked with elevated ridges, which form a regular 

 raised pattern, impossible to describe by words, but of 

 curious symmetry, forming three perfect pentagonal areas, 

 and parts of eight others surrounding them. 



This kind of sculpturing is most remarkable in a little 

 * Noteus quadricomis. 



