io6 Descriptive Zoology. 



projection, the foot, is found extending from the anterior 

 ventral margin ; but this will be at once, though not rapidly, 

 retracted, and the shell securely shut. 



The Enemies of the Clam. The question naturally arises, 

 " Why does the clam need such a strong protective cover- 

 ing ? " The working parts of the body are soft, the Latin 

 word mollis giving the name to the whole branch Mol- 

 lusca. Such a soft-bodied animal would naturally be the 

 prey of carnivorous animals. And further, since the clam 

 is slow in movement and has few and poorly developed 

 senses by means of which to become aware of the presence 

 of enemies, it is not surprising that it should be thus 

 securely protected. Among his most dangerous foes are 

 the raccoon, otter, mink, and muskrat, and probably other 

 mammals that frequent the water or prowl along the banks 

 of our streams. Muskrats open the shell by first gnawing 

 off the hinge, after which it is comparatively easy to open 

 the shell. Against its enemies the clam has, apparently, 

 but the one means of defense, namely, to shut the shell as 

 strongly as possible and to keep it shut till the coast 

 clear. Man, whether gathering specimens for study, seek- 

 ing pearls, or gathering the shells for buttons, is to be reck- 

 oned among the clam's enemies. 



How the Clam opens and shuts its Shell. Two l 

 cylindrical muscles pass directly across the body of th< 

 clam, connecting the two valves. One of these muscles 

 at the anterior end, the anterior adductor muscle, and th( 

 other, the posterior adductor muscle, is at the posterioi 

 end. The ends of these muscles are strongly attached to 

 the inside of the shell. When they shorten they bring the 

 two valves together and hold them with great force. 



For an inch or so along the dorsal margin the two valves 

 are held together by the elastic hinge ligament, which is 



