GENERA OF SHELLS. 95 



(&.) Outer lip smooth. 

 O. gibbosa, acicularis, spelta, birostris, volva. 



CYPRJEA. Shell oval or oval-oblong, convex, 

 margins turned inwards. Aperture longitu- 

 dinal, narrow, both lips toothed, effuse at both 

 extremities. Spire very small, scarcely ap- 

 parent. 



The shell assumes a very different appearance at dif- 

 ferent periods of growth. When young the aperture 

 is dilated especially at the lower part, is entirely with- 

 out indentations, and the right lip is short. In the mid- 

 dle stage of growth it acquires the general form of the 

 adult shell, but it has only its first layer of testaceous 

 matter, and the spire, though very small, is not en- 

 tirely covered, and its colors are still wanting. Without 

 attention to the varying form of the shell according to 

 age, we shall be liable to make three distinct species of 

 the same individuals. Sometimes the spire presents a 

 little pit, like an umbilicus ; sometimes both the mar- 

 gins are dilated, sometimes only one and sometimes 

 neither are prominent or inflated. 



C. cervina, exanthema, argus, testudinaria, Mauritiana, 

 mappa, Arabica, histrio, scurra,rattus, stercoraria, mus, ven- 

 triculus, aurora, tigris, tigrina, talpa, carneola. lurida, vilelius, 

 caput-serpentis, cinerea, zonata, sordida, icterina, miliaris, 

 variolaria, rufa, lynx, adusta , erosa, caurica, isabella, ocellata, 

 cribraria, turdus, olivacea, stolida, hirundo, undata, zigzag, 

 flaveola, sanguinolenta, poraria, ursellus, asellus, moniliaris, 

 stercus-muscarum,cicercula, lota.globulus, ovulata, helvola, 

 arabicula, staphylea, pustulata, nucleus, limacina, moneta, 

 obvelata, annulus, radians, oniscus, pediculus, oryzge, 

 coccinella, australis, albella. 



