THE PINNA AND THE CANCER. 3 



attended by a crab, ' his cancer friend ;' but why 

 it is called anchored I do not know, but cancer 

 is Latin for crab." 



'' Here is a species of Piwwff," said his father, 

 opening a cabinet; " and these silken threads are 

 the means by which it fastens itself to the rocks. 

 The animal is provided with a long foot, with 

 which it draws out the threads, or byssus. The 

 Pinna is sometimes called the silk-worm of the 

 sea. Lucy, do you know a univalve shell?" 



" Oh yes, many !" replied Lucy, " here are 

 rock-shells, cowries, limpets, and cones. I know 

 the difference between a cowry and a cone ; but I 

 am not yet acquainted with a multivalve shell — • 

 will you show me one.^" 



"■ Chiton, or coat of mail, is a good example," 

 said Mr. Elliot ; " Pholas is another genus of 

 the same division ; it has the appearance of a 

 bivalve. In the Chito7i are several lamiria, or 

 plates, which are connected by a membrane while 

 the living animal is in the shell ; the membrane 

 is pliant, and the inhabitant has the power of 

 contracting itself into a ball, when it would avoid 

 injury, like the insect millepes, that we find 

 under stones in damp places. (Plate 1.) The 

 curious barnacle-shell, Lepas, is another multi- 

 valve." (Plate 1.) 



" I think we cannot have a more agreeable 

 pursuit for our leisure hours," said Lucy, "than 



B 2 



