50 LESSON IX. 



course. Now look at this very singular shell. 

 (Murex haustellum.) 



Child. It has a long tube. 



Teacher. From what does it proceed ? 



Child. From the mouth. 



Teacher. Do you recollect any animals that 

 have a similar projection proceeding from their 

 mouths ? 



Child. Oh yes ; birds, their beaks are like this 

 part of the shell. 



Teacher. This projection in shells is also 

 called a beak, or rostrum, the Latin for beak. 



Child. The beak is hollow. 



Teacher. It is ; the interior is called the canal, 

 and the shells which have these beaks are said to 

 be canaliculated ; and when the aperture has not 

 a beak or canal, it is called entire. 



Child. Is the beak of any use ? 



Teacher. Yes, the animals which have this 

 beak have an elongated fleshly tube, which is in 

 some way connected with their breathing. 



Child. Many of the shells have projections, 

 some resembling thorns, some ridges, and some 

 rounded protuberances. 



Teacher. The projections resembling thorns 

 are called spines, and the shells which have them 

 are said to be spinous. The rounded projec- 

 tions are termed tubercles, and the shells on 

 which they appear are called tuberculous. The 

 ribs which are longitudinal rounded sutures form- 

 ed at the various growths of the shell, are called 



