6^ Shell Life 



to account for this unwholesome condition, but it 

 would appear to be due to their growth in the com- 

 paratively stagnant w^aters of harbours, or to their 

 being laden with spawn. In various parts of the 

 coasts of Europe, Mussels are in a sense cultivated by 

 placing boughs of trees on the mud, which become 

 covered thickly with Mussels. The boughs are 

 taken up after a few years and sold by weight. 

 The accompanying woodcut showing the various 

 parts of the animal will help to make clear further 

 descriptions of the bivalves. 



The large Horse Mussels are by most authors 

 separated from the genus Mytilibs and known by the 

 name of Modiola. Of these we have several distinct 

 species. Their shells are more oblong than wedge- 

 shaped, quite without teeth, and tlie b3^ssus though 

 much finer is also more ample. Instead of hanging 

 themselves up, they burrow, and some spin a kind of 

 byssal nest around themselves in which gravel and 

 other marine rubbish is mixed up. The affix 

 " Horse " si«:nifies that these Mussels are coarse and 

 unfit for food. 



The Common Horse Mussel (if. modi- 

 olus) may be distinguished readily from 

 the Mussel by the fact that the beaks 

 instead of being at the extreme pointed 

 end of the shell are at a slight distance 

 from it. The thick solid shell is purplish 



yellow in hue, but its true colour is dis- 

 common Horse >J ' 



Mussel (re- gulscd by thc dark brown epidermis 



duced) which, in young specimens, becomes 



drawn out into long fringing processes. As in the 



Mussel, the impressions of the mantle and muscles are 



