EXPLANATION OF PLATE XXVI. 



FIGURE 179. Mya areuaria, (p. 672;) with animal in extension, reduced to one-half 

 the natural size. 



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



181. Tagelus gibbus, (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 papillte en 

 larged. 



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



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



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



(The figures were all drawn from nature, by A. E. Yerrill.) 



