70 MACTRA. 



functions than those of the outward ligament; jfor 

 there are few, if any, instances, in which it is found 

 without the latter. In Mactra, in the pectinated 

 Ostrea, and in Mya, there are both ; but the inter- 

 nal tendon seems designed to give a firmer con- 

 nection and greater tenacity to the valves, where, 

 for want of a sufficiently deep insertion of the teeth, 

 some strong tie is requisite to prevent a lateral mo- 

 tion. Thus it does not exist in Tellina, Cardium, 

 or Venus. 



To /xaxrga, 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. 



