THE SHELL-FISH OF THE COAST. 53 



over the beaks, and in acidulated waters sometimes 

 nests of the epidermis alone will be found, the 

 limy parts having been completely dissolved away. 

 This species enters freely into brackish water. 

 A second species, smooth, and of much larger size, 

 measuring as much as six inches in length, is the 

 Modiola modiolus, a common form of moderately 

 deep northern waters. 



