PALEONTOLOGY. 

 PLATE XI. 



Page. 

 YOLDIA EVANSI M. & H 409 



Fig. 1. Enlarged view of a cast of a left valve, showing the teeth, muscular imprints, and 



pallial line. 

 Fig. 2. Enlarged outline cardinal view of a specimen retaining the shell, showing the 



groove extending along the hinge. 



NUCULANA SUBEQUILATERA Whitf 408 



Fig. 3. Enlarged view of the left side of an internal cast, showing the form and muscular 



imprints. 

 Fig. 4. Enlarged cardinal view of the same, showing the impression of the teeth. 



NUCULA PLANTMARGINATA M. & H .- 406 



Fig. 5. View of the left side of a partially exfoliated specimen, showing the general form. 

 Fig. (>. Enlarged cardinal view of the same, showing the impression of the hinge, along 

 which the shell is more completely removed. 



NUCULANA BISULCATA M. & H 407 



Fig. 7. Enlarged view of a specimen, showing the form and surface markings. 



Idonearca shumardi M. & H 405, 



Fig. 8. View of the right side of a specimen ofmediuni size, showing the form and general 



character. 

 Fig. 9. Cardinal view of the same, showing the cartilage area. 

 Fig. 10. Posterior view of an internal cast, showing the impressions of the ridges bordering 



the muscular imprints. 

 Fig. 11. View of a large individual having the valves a little displaced and showing the 



posterior hinge-teeth. 



Crassatella subquadrata Whitf 412 



Fig. 12. View of the right side of the cast, natural size. 



Astarte evansi H. & M 413 



Fig. 13. View of the right side of an internal cast, showing muscular scars, pallial line, and 

 crenulated margin. 



LUCINA VENTRICOSA H. & M 410 



Fig. 14. View of the right side of a well-formed specimen of medium size, showing the 



general character of the species. 

 Fig. 15. < 'ardinal view of the same, showing the cardinal depressions and ligament. 

 Fig. 16. View of an internal cast of a large individual. 



LUCINA (DlPEODONTA ?) SUBUNDATA H. & M 411 



Fig. 17. View of the right side of oue of the larger individuals, showing the narrow, curved 



posterior slope and anterior furrow. 

 Fig. 18. Cardinal view of the same, showing the ligament and depressions. 



Ltjcina occidentals Mort- 409 



Fig. 19. View of a well-formed specimen of typical form. 



Fig. 20. Cardinal view of the same, showing the almost obsolete lunule. 



Fig. 21. Internal cast of a small individual. 



Thetis circulaius M. & H 417 



Fig. 22. View of the right side of a specimen of ordinary form. 



Fig. 23. Cardinal view of a similar specimen, showing the incurved beaks and the convexity 



of the valves. 

 Fig. 24. View of a partial cast, showing the character of the pallial line and sinus. 



Dosinia missouriana Mort. ? 416 



Fig. 25. View of the left side of a specimen referred to this species. 

 Fig. 26. View of the opposite side showing the i>allial sinus. 



Leiopisiiia (Cymella) Meeki Whitf ... 4]8 



Fig. 27. View of a right valve of the species, natural size. 



Fig. 28. Cardinal view in outline, showing the areas bordering the hinge, over which the 

 rays and concentric folds do not extend. 



Thracia subgracilis Whitf 419 



Fig. 29. View of the right side of the specimen, showing the form, and the slit in the beak. 

 Fig. 30. Cardinal view of the same, showing a slight twisting of the valves in the crooked 

 hinge line. 



NEiERA MOREAUENSIS ? M. & H 420 



Fig. 31. Enlarged view of a left valve, showing the features as described. 



