They by no means confine their work to the orchard, but all kinds of trees and shrubs are alike visited. In thus performing the duty assigned them by Nature they are of inestimable service to man.
Addie L. Booker.
THE COWRIES AND SHELL MONEY.
Among marine mollusks none stand so favorably in the eyes of collectors or are so beautiful as the Cypraeas, or Cowry shells. With their glossy coats and varied colors they are indeed gems of the ocean, and it is little wonder that the conchologist has placed them first among the many families of marine shells.
The name Cypraea comes from Cypris, one of the names of the goddess Venus. About two hundred recent species have been described and they are found in nearly all parts of the world, though more numerous in the tropics and sub-tropics, where they live on coral reefs and under rocks. As in many other genera of shells the Cowries living in the tropics are more brilliantly colored than those from more temperate climes, a condition due to the large amount of sunshine and high temperature, both of these factors being essential to the secretion of color in the pigment cells of the animal.
The animal which inhabits a Cowry shell is a curiosity. The foot is large and spreads out in a wide mass, enabling the animal to glide along quite rapidly. The mantle lobes are folded over the back of the shell and are beset with many little tuft-like organs which stick out like young shoots on a plant. The mouth is placed at the end of a rather long snout or rostrum and the eyes are upon the outside of two long, tapering tentacles, about one-third the distance from the body. When the shell is young it is covered with a thin epidermis and has a thin, sharp outer lip, like some snails, but when it is full grown the outer lip rolls inward, becomes toothed or ridged, as does also the inner lip, and the aperture becomes a long and narrow slit reaching from the apex to the base of the shell. The mantle lobes, which are inconspicuous in the young shell, becomes larger and are reflected over the back, depositing coat after coat of shelly enamel until the first pattern of the shell, as well as the epidermis, is covered with a secondary, shining coat. On most Cypraeas there is a line of paler color, showing where the two lobes of the mantle meet on the back.
Like many other mollusks the Cypraea is able to dissolve the internal whorls and thus enlarge the capacity of its shell. This is also true of Conus, and Murex, and some other marine snails dissolve the spines which may be in the way when increasing the size of the whorls. The older naturalists, Lamarck and Bruguiere, believed that the Cypraea was able to dissolve its outer lip after it had been rolled over and toothed, but this theory has been proved to be incorrect. They founded their belief on the fact that some individuals of the same species were larger than others. This, however, is due simply to individual variation.
The beautiful colors so much admired are deposited by the reflected mantle and their variety is almost endless. Some are perfectly plain, white, brownish, yellowish or orange, others are spotted with red, white, brown, drab or black, and still others are variously banded. The eyed-cowry (Cypraea argus) has large, dark brown spots on a lighter background.
In form and sculpture the Cowries present a rather wide range of variation. The typical form is more or less cylindrical, or pyriform, while others are flat, oval or egg-shaped. The surface varies from smooth to spirally lined and pustulose. In size they vary from the little Trivia exigua, scarcely one-fourth of an inch long, to the huge Cypraea testudinaria, nearly five inches in length.
Many of the larger species, like the tiger cowry (Cypraea tigris) and the black cowry (Cypraea mauritiana) have been household ornaments for centuries and have also served as playthings for young children, who have held them to their ears to “hear the sound of the roaring sea.”