PLATE 56. 



p»g» 

 Figs. 1-5. Leiorhtnchus mvsia 357 



(Tlie figures of this species are all enlarged to two diameters.) 

 1-3. Dorsal, ventral and profile views of a specimen of the ordinary size and characters of 



the sjiecies. 

 4. Dorsal view of another individual, having a less prominent beak and duplicate plications. 

 ' 5. Dorsal view of an unusually large specimen, with sloping cardinal line. 



Figs. 6-21. Leiorhynchus limitaris. 356 



6-8. Dorsal and ventral views, and profile of a specimen of the usual form and size of those 

 from the limestones in the Marcellus shale of Schoharie Co., N. Y. 



9. Ventral view of another specimen, with fewer plications in the sinus. 

 10- 12. Dorsal, profile, and front views of a somewhat larger specimen. 



18, 14. Profile and front views of a very gibbous form, having numerous plications. 

 15-19. Dorsal ventral, profile, cardinal and front views of an unusually large and broad 

 individual. 



10. Front view of a very gibbous form, which is abruptly elevated in firont and having only 



three plications in the sinus. 



21. Dorsal view of a flattened specimen, from the thinly laminated black shales. 



Fig8. 22 - 25. Leiorhynohus dubius 364 



22. Dorsal view of a specimen, with a slightly elevated mesial fold. 



23-25. Dorsal, ventral and profile views of a specimen, with a more distinctly elevated 

 mesial fold, and stronger plications. 



Figs. 26-40. Leiorhynchus multicosta 858 



26. Dorsal valve of a young individual. . 



27. Dorsal valve of a larger individual. 



28. Dorsal valve of a si)ecimen of medium size. 



29. Cardinal view of a gibbous specimen. 



30. Dorsal vie.w of a crushed individual of ordinary size. 



31. 32. Ventral valves of elongated specimens, showing considerable variation in the plications. 

 88. Cast of a dorsal valve of unusually large size. 



34, 35. Dorsal and ventral views of a young and much elongated specimen, from Widder, C. W. 

 36-40. Dorsal, ventral, profile, cardinal and front views of a full grown and well preserved 

 individual, from the Hamilton shales of Canada. 



FigB. 41 - 43. LEioRHYNcntTS iris 360 



41 - 48. Dorsal, ventral and profile views of the specimen described. 



Figs. 44 - 49. Leiorhynchus quadrioostata 357 



44. Dorsal valve of a crushed and flattened individual of small size. 



45 -48. Views of dorsal valves of this species, showing gradations in size. 



49. Ventral valve of a large individual. 



