250 ZOOLOGY. 



forate whilst in their young state, and continue to enlarge 

 Iheir habitation or prison, as they encrease in bulk ; they all 

 emit a phosphoric light, most evident, whilst the animal is 

 in a living state. 



** Bivalves. Shells in two parts united hy a cartilagi- 

 nous hinge. 



4. Mya, Gapes. Inhabitant an Ascidea. 



Shells gaping at one or both ends ; hinge with generally 

 one thick, strong, broad tooth, which is not inserted 

 into the opposite valve. Plate 4, fig. 5. 



These are found on the margins of the sea and rivers, and 

 are discoverable by a small hole or aperture in the mud or 

 sand ; some of the kinds are used as food, and others 

 produce pearls in considerable abundance. 



5. Solen. Razor-Shell. Inhabitant an Ascidea. 



Shells oblong, gaping at both ends ; hinge with one or two 

 subulate teeth, which are not inserted into the opposite 

 shell. Plate 4, fig. 6. 



The Solens penetrate the sands of the sea shore, in a per- 

 dendicular direction, to the depth of six to twelve inches, and 

 are easily discovered by an indentation in the sand ; some of 

 the kinds are edible. 



6. Tellina, Bent-Wedce. Inhabitant a Tethys. 



