PLATE XXXI. 
Mytilarca (Pjlethomytilus) oviformis. 
Page 255. 
See Plate 87. 
Fig-. 1. A left valve of a young shell of elongate form. 
Hamilton group. Cayuga lake, N. Y. 
Fig. 2. A left valve of the ordinary size, showing the striated hinge-area and three posterior teeth on the 
wing which are not sufficiently marked in the lithography. 
Hamilton group. Cayuga lake, N. Y. 
Fig. 3. A right valve showing the strong ligamental area. 
Fig. 4. A more elongate form with attenuate beak. 
Hamilton group. York Centre, Livingston Co., N. Y. 
Fig. 5. The anterior side of a compressed specimen preserving the valves in contact at the hinge, but 
widely parted below. 
Hamilton group. Greneseo, Livingston Co., N. Y. 
Fig. 6. A large right valve widened below by compression. 
Hamilton group. Seneca lake, N. Y. 
Fig. 7. A cast of a small elongate right valve. The beak has been removed to show the ligamental area; 
the three oblique lateral teeth are seen on the post-cardinal angle. 
Hamilton group. Canandaigua lake, N. Y. 
Fig. 8. A large, broad right valve showing an unusually short hinge-area. 
Hamilton group. Bellona, Yates Co., N. Y. 
Gosselettia triquetra. 
Page 265. • 
See Plate 87. 
Fig-. 9. A view of the left valve of a young individual of this species. 
Fig. 10. The right side of a very ventricose specimen preserving the natural form. Supposed to be the 
original specimen. 
Figs. 11, 13, 14. The Left, cardinal and posterior views of a specimen preserving the natural convexity 
and showing the posterior teeth of the left valve. 
Hamilton group. Onondaga Co., N. Y. 
Fig. 12. The anterior side of a similar specimen showing the anterior muscular impressions. 
Hamilton group. Onondaga Co., N. Y. 
Fig. 15. A partial cast of a left valve. The beak has been removed to show the strong anterior teeth and 
anterior muscular impression. 
Hamilton group. Fultonham, Schoharie Co., N. Y. 
Fig. 16. A large left valve preserving the surface markings and the ligamental area. 
Hamilton group. Fultonham, Schoharie Co., N. Y. 
Fig. 17. A large right valve. 
Hamilton group. Madison Co., N. Y. 
