BULLA

(LaL) A stud or bo , but more particularly an ornament in the shape of a heart, worn round the neck by noble Roman children till they ■■ en years old; when they a umed the manly dre of the toga, and I the bulla as a consecrated offering to the lore* or household gods. Du'i.la. (I.at. bulla, a bubble.) A genus of Acerous Qaatropodoui Molluake, the shell of which is more or leas ir Inflated like a bubble; having no visible or proipire, which is concealed by the large external whorl, which is elevated above the rest. The columella makes a convex prominence, which gives a crcscentic form to the aperture of the shell; the animal breathes by gills, but lias no respiratory tube or siphonj and consequently the ■Mrgtn of the aperture of the shell is entire, or without a icanal. All the species of bulla are remarkable for a shelly apparatus of three pieces, which converts the itomach into a gizzard or triturating cavity. These gastric as have been described as a bivalve shell of i new genu*. [s. 187]