PLATE 74. 



Fig. 1, 2. 682. 31. Orthis interstriata. ( Pag. 326.) 



1 a. The interior of the ventral valve, showing regularly dichotomous strias. 

 • 1 6. The stria enlarged. 2 a. The dorsal valve of a smaller specimen. 



2 b. The surface enlarged, showing the interstitial striae. 



Fig. 3. 683. 27. Lept^na . ' ( Pag. 826.) 



3 a. A specimen showing the form of the shell. 



3 b. An enlargement, showing the thin radii and connecting concentric lines. 



Fig. 4, 5. 684. 28. Leptjena bipartita. .( Pag. 326.) 



4 a. The interior of the ventral valve, with the dental laminaj worn off. 



4 6. An enlargement from the surface of this specimen. 



5 a. The impression of the dorsal valve, with some portions of the shell remaining. 



Fig. 6. 685. 2. Strophodonta textilis. (Pag. 327.) 



6 a. The ventral valve described. 



6 b. The hinge-line enlarged, showing impressions of the crenulations. 



6 c. A further enlargement of a portion of the same, showing the crenulations. 



6 d. A portion of the surface enlarged, showing the fine concentric strise. 



Fig. 7, 8. 686. 10. Spirifer . ( Pag. 327.) 



7. The dorsal valve of a specimen, showing evidences of five plications on each side of the mesial sinus. 

 8 a, b, c. A very convex dorsal valve, where the evidences of plications are more obscure, though the sur- 

 face still preserves marks of concentric striae. 



8 d. A smaller specimen liaving the angle partially covered by the stone. 



Fig. 9. 623. 6. Spirifer crispus. ( Pag. 328.) 



9 a - A . Different views of several specimens of this shell , showing very clearly its identity in form with those 



figured on PI. 54, the latter having the plications more strongly developed. 



Fig. 10. 687. 58. Atrypa nucleolata. ( Pag. 328.) 



10 a, b, c. Views of the ventral valve in several specimens of different size. 

 10 d, e, f. Front views of the same specimens, showing the indentation. 



10 g, h. Dorsal valve and cardinal views of another specimen. 



10 I, fc. Dorsal and ventral veiws of a larger individual, where the indentation is scarcely perceptible. 



10 Z, m. Profile views of fig. 10 i and fig. 10 fe. 



Fig 11. 6S8. 59. Atrypa lamellata. ( Pag. 329.) 



11a. Ventral valve of a full grown specimen. 11 b. Several plications enlarged, 



11 c, d. Ventral and front view of a smaller specimen. 



11 e, /. A specimen showing scarcely any sinus or elevation. 



11 g, h. Profile views of different specimens, the lower figure perhaps flattened from compression. 



11 %. Dorsal valve of an individual in which the plications are worn smooth. 



11 fc. Profile showing the elevation of the plications. 



Fig. 12. 689. 60. Atrypa . ( Pag. 330.) 



12. A fragment of .stone, on which are grouped several specimens of the preceding species, with a single one 

 of this species in the centre. 



