CHAPTER XXIL 
NACRE AND PEARLS. 
NACRE is that beautifully smooth, white, and iridescent lining with 
which some shells are internally coated; it is the same material 
which composes the pearl. Though many shells are lined with 
nacre, yet one bivalve, the MWZeleagrina margaritifera, which is 
often called the Pzztadine, secretes the substance so plentifully that 
it deserves its name—the mother-of-pearl shell. 
PINTADINE, OR MOTHER-OF-PEARL. 
(Meleagrina margaritijera.) 
This mollusk moors itself to the bottom of the sea by a strong 
brown byssus. The valves of the shells are irregularly rounded, 
and when the animal is only a year or two old, the foliations are 
thin and even; its shell is streaked with bands of green, which 
radiate from the summit, and branch off towards the edges of the 
valve. But as years pass, the shell becomes rugged, the bands 
disappear, and the whole takes a uniform blackish tint. Eight or 
ten years bring the mother-of-pearl to perfection ; the shell is then 
about six inches in diameter, and one and a quarter inch thick. 
Nacre is very hard, and exhibits a resplendent surface ; its 
appearance is not unlike floss silk, faintly tinted with azure, and 
