PLATE 31 B. 



Fig. 1. 145. 8. Lbptjena altebnistriata. (Pag- 109.) 



1 o. Dorsal valve of a large specimen, showing a very regular alternation in the size of the striae. 

 1 b. Ventral valve of the same specimen, the stria: being regular and uniform in size. 



1 e. A smaller specimen, presenting a greater extension of the cardinal extremities, and an irregular alterna- 



tion of the striae upon the surface. 



Fig. 2. 146. 9. LfiPTiENA sekicea. (Pag. 110.) 



2 a, b. The form and surface of the shell are perfectly preserved in this specimen, both valves of which have 



distinct larger strise alternating with several smaller ones. 

 2 e, d. The opposite valves of another specimen, showing the equal strise and a few concentric lines of growth. 

 2 e. Interior of the ventral valve, showing two wiiiglike papillose callosities for the visceral attachment. 

 2/, shows a variation from the preceding internal structure. 

 2 g. Interior of the convex valve, showing the visceral impression, margined by a sharp elevated ridge. 



2 A. View of the cardinal area of the convex valve, showing the deltoid aperture which is partially closed. 



Fig. 3. 147. 10. LeptjENA FiLiTEXTA. (Pag. 111.) 



3 a. Ventral valve of a large specimen. 3 6. Cardinal area. 3 c. Interior of the dorsal valve. 



3 d. Dorsal valve of a smaller specimen. 3 e. Cardinal view of the same. 

 3/. An enlarged portion of the surface, showing the textile character. 



Fig. 4. 148. 11. Leptxna PLANCMBONA. (Pag. 112.) 



i a k.b. Views of the two valves ; the ventral one 4 showing some strong imbricating lines of growth. 



4 e. Cardinal view, showing the nearly linear area and closed foramen. 



4 d. Interior of the concave valve. 4 e. Lateral view of the shell. 



Fig. 6. 149. 12. LEPT.ENA deflecta. (Pag. 113.) 



5 a. Dorsal valve of the specimen. 5 6. Cardinal area of the same. 



Fig. 6. 150. 13. LBPT.ENA RECTA. (Pag. 113.) 



6 a. View of the ventral valve. * 6 6. Cardinal view of the same shell. 



Fig. 7. 151. 14. LEPT.a:NA planoconvexa. (Pag- 114.) 



7 a. View of the dorsal valve, with one of the cardinal extremities produced beyond the other. 



7 6. A smaller specimen. 7 e. Profile view of the shell. 7 d. Cardinal view of the first specimen. 



Fig. 8. 152. 15. LEPT.ENA TENUILINEATA. (Pag. 115.) 



Fig. 9. ' 153. 16. LEPT.ENA subtewta. (Pag- 115.) 



9 o. View of the dorsal valve. b. Interior of the hinge margin. 



Fig. 10. 154. 17. Leptmva {Species undetermtTied). (Pag. 116,) 



10 a. Ventral valve, showing the equal radiating striae. 10 b. Dorsal valve, with unequal striae. 



10 e. Cardinal area, and the same enlarged, showing the open foramen and imperforate beak. 



