EXPLANATION OF PLATE XXVI. 
Fictre 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. 675;) with animal, the siphons not fully extended, 
one-half natural size. 
122.—Ensatella Americana, (p. 674;) with animal extended, one-half natural 
size. The figure at the right shows some of the terminal papille en- 
larged. 
183.—Teredo navalis, (p. 669;) enlarged two diameters. 
184, A.— Venus mercenaria, (p. 681;) natural size. 
184, B.—Maulinia lateralis, (p. 680;) natural size. 
(The figures were all drawn from nature, by A. F. Verrill.) 
