8 



MULTIVALVES. 



PHOLAS. 



custom of adhering to tlie crags of rocks, and other pro? 

 J€ctions in the sea. 



LEPAS. 



PHOLAS.— Ston e-pi ercer. 



Animal— an Ascidia : Shell hivalve, divaricate^ with several 

 smaller t differently-shaped accessory valves at the hinge: 

 — hinges recurvedy united hy a cartilage ; in the inside, 

 beneath the hinge, is an incurved tooth. 



It appears that hitherto only twelve species of this ge- 

 nus have been enumerated, and some of tliose are so alike, 

 that in many instances, they might be considered as mere 

 varieties rather than different species ; however, they all 

 possess sufficient determinate characters, to prevent any 

 admixture with the genera of Bivalves. 



