ANOMIA ANTIQUE LAMP. 181 



dage, having a dilated base ; this is in fact only a 

 prolongation of the adductor muscle of the ani- 

 mal ossified at its outer extremity. When the 

 molluscum contracts the muscle, the dilated 

 portion is drawn over the perforation of the flat- 

 tened valve and covers it, acting as an opercu- 

 lum. So firmly are the shells fixed by this organ, 

 that they cannot be removed from their retreat 

 without destructive violence, the ligament and 

 operculum being left on the rock to which they 

 were cemented. The form of the Anomia, like 

 that of all stationary shells, is very irregular, be- 

 ing usually modified by the substances to which 

 it adheres. The prevailing colour, of this genus 

 is a dingy yellow, or dusky white ; the shells are 

 generally thin, fragile, delicate, and would be ill- 

 fitted to contend with the dangers of their dwel- 

 ling in the boisterous ocean, had not He who 

 placed them amid its perils, exercised his com- 

 pensatory providence, and anchored them se- 

 curely in its depths. 



The other family of this genus now bears the 

 name of Terebratula. The shells which it con- 

 tains are distinguished by the graceful elegance 

 of their form, which resembles a Grecian lamp, 

 and from hence they are called the Antique 

 Lamps. The concave valve of the Terebratula 

 has its beak produced, curved over the other 

 valve and perforated at the apex ; the smaller 

 valve is furnished with two slender shelly pro- 

 cesses which are sometimes short, simple, and 

 recurved ; sometimes long, branching and cros- 

 sing each other ; their use is not ascertained, but 

 16 



