OF CONCHOLOGY. 45 



cies of this genus are described ; fif- 

 teen species have been discovered in 

 the British seas. 



Genus 3d.— PHOLAS. Animal an 

 Ascidea; shell bivalve, divaricate, with 

 several lesser, differently shaped, ac- 

 cessory ones, at the hinge ; hinges 

 recurved, united by a cartilage ; in the 

 inside, beneath the hinge, is an in- 

 curved tooth. Linn.Sy st. 302. Plate 

 5th, fig. 3d. 



Habitation. Pholades are found 

 below high water-mark, burrowed in 

 hard clay, lime-stone, or sometimes 

 free-stone, and also wood, which they 

 perforate in their younger state, and 

 as they increase in size enlarge their 

 habitation. 



The phosphorescent properties of 

 the Pholades are very remarkable ; it 

 contains a liquor which shines with 

 uncommon splendour in the dark, and 

 illuminates whatever it touches, or 

 happens to fall upon. See Memoirs 

 of the French Academy, 1712. 



