60 LINN^AN GENERA. 



Many of the Cones are very beautiful. Some of them bring the 

 highest prices of all shells, from their great rarity. One species, the 

 Cedo Nulli of Lyonet, is valued at one hundred guineas. Cones are 

 covered with an epidermis, and it is not till this is removed that their 

 beauty can be seen. Their surface is highly polished, contributing 

 much to heighten the delicate and glowing tints which are diffused 

 over some of the finer species in an infinite variety of undulations, 

 clouds, spots, and bands. 



Genus 2i — CYPRiEA. 



Animal a Slug; shell univalve, involute, sub-ovate, 

 smooth, obtuse at each end; aperture effuse at both ex- 

 tremities, linear, extending the whole length of the shell, 

 and dentated or toothed on each side. 



Linnaeus divides the genus Cyproea into four families : *mucronate, 

 or pointed ; **obtuse, and viithout any manifest spire ; ***umbili- 

 cated, or with a small perforation ; *«**mai'ginated. 



The genus Cypraea consists of beautifully coloured, and very highly 

 polished shells. It is said, that they leave their shells annually, and 

 construct new and larger ones. But we have not been able to ascer- 

 tain this point as a fact. 



They live in sand at the bottom of the sea ; the animals are provided 

 with a membrane, which they throw over their shells, and which pre- 

 serves the fine polish, and prevents other testaceous bodies from fixing 

 on them. The Cypraeae have only been found to inhabit the ocean. 



Cypraa Uropcsa The European Cypr^a. Plate 



VIII. tig. 21. With numerous transverse furrows, tumid 

 on the back, pale purple or whitish, and generally with 

 three dark blackish-brown spots. Half an inch long. In- 

 habits the British seas. 



Genus 22.-BULLA. 



Animal a Limax; shell univalve, convolute, and unarmed 

 with teeth; aperture a little straitened, oblong, longitudinal, 

 very entire at the base ; pillar oblique and smooth. 



Bulla Catena.— The Chain Bulla. Plate VIII. fig. 

 22. (BuUaea Catena, Lamarck.) Ovate, white, pellucid, 

 with minute chain-like transverse striae ; aperture extremely 

 large, obtuse at the top, with a single volution, and one- 

 fourth of an inch long. Inhabits the British seas. 



