132 SEA-SHORE LIFE 



esting relative of the massel family. It is common in shallow 

 water along the sandy shores of the West Indies and Florida, and 

 extends as far north as the North Carolina coast. Each valve of 

 the shell is fan-shaped, with a sharp-pointed apex and a wide, 

 sharp-edged margin. It attaches itself by means of a strong 

 byssus-thread to a rock beneath the sand, and the broad edge of 

 the shell projects above the surface of the ground. The valves of 

 the shell open and shut rythmically, thus creating a current of 

 water over the gills and drawing minute organisms into the ever 

 open mouth. The razor shells, owing to their great abundance, 

 and sharp edges, render wading with bare feet all but impossible 

 on parts of the Florida coast. 



THE FRESH-WATER MUSSELS. 



There are fully (500 species of fresh-water mussels in the 

 streams of the United States, and more than three-quarters of them 

 live in the Mississippi and its tributaries. The shells are usually 

 elongate and covered with a thick outer skin. The two valves of 

 the shell are similar each to each, and there is a well developed 

 foot, by means of which the animal ploughs along through the mud 

 making a deep furrow with only about one-half of the posterior end 

 of the shell projecting. There are two large openings in the man- 

 tle at the posterior end of the shell, and these openings are usually 

 beautifully fringed. The one nearest the hinge side is the anal 

 aperture while the other serves to admit water and minute organisms 

 into the gill chambers. Although usually dull brown or greenish 

 in color on the outside, the inside of the shells are beautiful, some 

 being purple-black, others silvery white, golden copper color, salmon- 

 pink or yellow. On this account they are highly prized for the 

 manufacture of buttons, and this industry on the Mississippi alone 

 is worth $40,000 annually. Valuable pearls are also obtained from 

 these mussels. 



The eggs of the fresh-water mussels are carried in pouches 

 between the layers of the outer gills, and there they remain until 

 they have developed a bivalve shell, the lips of which are armed 

 with sharp, hook-like spines. The little mussel is then cast out and 

 drops to the bottom where it comes to rest with the open valves of 

 its shell upwards, and then it thrusts out a long, glutinous, thread 



