EXPLANATION OF PLATE XXVI. 



Figure 179.— Mya areiiaiia, (p. 672 ;) with animal in extension, reduced to one-half 

 the natural size. 



180. — Angulus tener, (p. 677 ;) animal reduced one-half. 



181._Tagelus gibbns, (p. 675;) 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 papilh-e en- 

 larged. 



183.— Teredo navalis, (p. 669;) enlarged twt) diameters. 



184, A. — Venus mercenaria, (p. 681 ;) natural size. 



184, B.— Mulinia lateralis, (p. 680;) natural size. 



<The flgiirea were all drawn from nature, by A. E. Verrill.) 



