EXPLANATION OF PLATE XXXI. 
FIGURE 253.—Crenella glandula, (p. 695.) 
234.—Mytilus edulis, (p. 692.) 
235.—Modiolaria corrugata, (p. 694.) 
236.—Modiolaria nigra, (p. 694.) 
237.—Modiola modiolus, (p. 693.) 
238.—Modiola plicatula, (p. 693.) 
(All the figures are of natural size, and from Binney's Gould, drawn by E. S, Morse.) 
