OSTREADiE. 
353 
Another remarkable species, Malleus vulgaris (Fig. 1 44) is a rare 
s hell, much valued and much sought after by amateurs and dealers. 
The beautiful diaphanous nacre which embellishes the interior of so 
tt>any ornamental cabinets are principally produced by the animal 
^habiting the Meleagrina, a bivalve, sometimes designated the pinta- 
lfle > or mother-of-pearl shell. This bivalve moors itself to the bottom 
the sea by a strong byssns of a brownish colour. The door posts 
lie shells are irregularly rounded in their young days ; they are 
eternally lightly foliated, and ornamented with bands of green and 
^ite, which spring from the summit in rays, and afterwards break 
^ into two or three slightly scattered branches. In old age they 
■^oine rugged and blackish. The shell is in its perfection when 
^ J °Ht eight or ten years old, then - size being then about six inches in 
at ueter, with a thickness of about an inch and a quarter. 
Nacre is the hard and brilliant substance with which the valves of 
^ftaiu shells are lined in the interior. This substance is white, 
slightly azure, and more or less iridescent. Most of the bivalves 
ar ° supplied with nacre ; some of them even yield a blue, or blue 
violet pigment. The iridescent Haliotis iris, for iustance, is an 
Jerald-greenish blue of changing colour, with reflections of a purple 
Vl °let. Turbo argorastymus (Linnaeus) presents a mouth of bright 
Si Nery hue, while Turbo chrysostomus appears in all the glory of 
^ ; but the Pintadine yields the purest white nacre, as well as the 
uniform, and especially the thickest. This product owes its 
lant and delicate appearance to the play of light on it in its 
A'hly_poij s hed state. For practical purposes the nacre is separated 
ti' ,tQ Ike shell with an instrument ; sometimes all the exterior part of 
® shell being dissolved away from the precious substance, leaving 
y the naked bed of nacre. 
u t the most interesting of all the nacre-bearing shells is the pearl 
jSti 
of 
Pearls 
SQj,. 
(■ Meleagrina margaritifera), the exterior, as well as the interior, 
"'kich is represented in Fig. 145. In the interior of the shell 
are sometimes found so fine and so beautiful that they are only 
'‘of P asse< ^ ky the diamond. This shell is nearly round, and greenish in 
! a ,lr on the outside ; it furnishes at once the finest pearls, under 
^able circumstances, and the nacre so useful in many industrial 
f ‘ kme pearls and nacre have, in short, the same origin. The 
la vests the whole interior of the shell of Meleagrina margariti- 
