EXPLANATION OF PLATE XXVI. 
FiGure 179.— Mya arenaria, (p. 672;) with animal in extension, reduced to one-half, 
the natural size. 
180.—Angulus tener, (p. 677;) animal reduced one-half. 
181.—Tagelus gibbus, (p. 6753) with animal, the siphons not fully extended,. 
one-half natural size. 
182.—Ensatella Americana, (p. 674;) with animal extended, one-half natural 
size. The figure at the right shows some of the terminal papill en- 
larged. 
183.—Teredo navalis, (p. 669;) enlarged two diameters. 
184, A.—Venus mercenaria, (p. 681;) natural size. 
184, B.—Mulinia lateralis, (p. 680;) natural size. 
(Lhe figures were all drawn from nature, by A. E. Verrill.) 
