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, «2 common form of moderately 
deep northern waters. 
