PLATE XIY 



Genus Tellinopsis. 



Fig. 1. A view of a subequilateral left valve of T. siihemarginata (= Nuculites hu1> 

 emarginatus Conrad); from the Hamilton group. 

 " 2. View of an inequilateral right valve, showing a stronger posterior sulcus. 

 The two represent nearly the extremes of form noticed in the species. 



Genus Cypricardinia. 



Figs. 3, 4. Views of a left and a right valve of C. planulata {= Pterinea planulata 



Conrad). 

 Fig. 5. View of a cast of a right valve, showing the large adductor muscle scars, and 



the strongly marked pallial line. 

 " 6. Cardinal view of the same individual, showing the inequality of the two 



valves. 



Genus Microdo?:. 



Fig. 7. View of the interior of M. tenuistriata H. & W., as obtained by gutta-percha 

 from the natural cast, showing faintly the features of the hinge, the an- 

 terior muscular impression, and a portion of the pallial line. 

 " 8. Cast of a right valve of M. bellustriata showing the cardinal teeth and anterior 

 muscular scar. 



Genus Pal a na tin a . 



Fig. 9. View of the right side of P. typa, showing the inequality of the valves, the 

 beak of the left projecting above that of the right. 

 " 10. View of a smaller left valve, showing the posterior umbonal sulcus. The 

 cardinal extremities of this specimen are more rounded than usuaL 



Genus Mytilarca. 



Fig. 13. Cast of a left valve of M. Chemungensis (= Inoceramus Chemungensis Con7: 

 Jour. Acad. Nat. Sci., Phila., vol. viii, p. 245). The cardinal and lateral 

 teeth are plainly indicated, as also the striations of the ligameutal area. 

 " 11. Cast of a more elongated variety. 

 " 18 Interior of the left valve, as obtained from an impression left in the shale. 



Genus Modiomorpha. 



Fig. 14 Interior of a left valve of M. cortcentrica (= Cypricardites concent rica Cow^ 

 rad) — the view obtained partly from the actual shell and partly completed 

 in gutta-percha. The figure shows the strong cardinal tooth of this valve, 

 and the adductor muscular impressions and pallial line. 



" 15. View of the exterior of a left valve, showing the ordinary form. 



" 16. Cardinal view of a vertically compressed specimen, showing the escutcheon 

 and form of the ligament, as preserved on the specimen. 



Genus Gontophora. 

 Goniop7iora, Murch. Siluria. p. 

 Fig. 17. View of a right valve of O. rvgosa (= Cypricardites rugosa Conr.), showing 

 the general external form of the shell. 

 " 18. View of the interior of a right valve of G. Hamiltonensix, showing the cav- 

 ity for the reception of the tooth of the left valve. The figure is made 

 from a gutta-percha impression of the natural mold. 



