56 MACTRA. 



outward ligament ; for there are few, if any, in- 

 stances, in which it is found without the latter. 

 In Mactra, in the pectinated Ostrea, and in Mya, 

 there are both; but the internal tendon seems 

 designed to give a firmer connexion and greater 

 tenacity to the valves, where, for want of a suffi- 

 ciently deep insertion of the teeth, some strong tie 

 is requisite to prevent a lateral motion. Thus it 

 does not exist in Tellina, Cardium, or Venus. 



To ftdxrga, a kneading-trough, we can trace but 

 little resemblance in our Mactra. The word was, 

 however, no doubt, at first selected for some good 

 reason of which we are now no judges. 



