PLATE 54. 



Fig. 1. 621. 4. Spirifer BiLOBus. (Pag. 260.) 



1 a, b. Ventral and dorsal view, where the extremities of the hinge-line are scarcely extended. 



1 c, d. Another specimen, wliere the extremities of the hinge-line are auriculate. 



1 e. Front view of a specimen, showing the bilobate character. 



1 /, g. Profile views of two specimens, one of which is mucli more convex than the other. 



1 h, i. Enlarged fignres of a specimen, representing the prevailing form. 



1 k. Interior of the ventral valve. 



Fig. 2. 622. 5. Spirifer sulcatus. (Pag. 261.) 



2 a. A small specimen, having the cardinal extremities scarcely extended. 



2 6, c. Views of specimens where the cardinal line is extended into mucronate points. 



2 d. An unusually large specimen, having the hinge-line less extended than the preceding. 



2 e. A specimen where the length and breadth are nearly equal. 



2 /. Front view of fig. 2 6. 2 g. Front view of 2 e. 



2 h, i. Profile views of different specimens. 



2 k. An enlargement of the surface, showing the longitudinal striae crossing the lamellae. 



Fig. 3. 623. 6. Spirifer crispus. (Pag. 262.) 



3 a, 6, c. Ventral views, presenting tlie ordinary characters of well preserved specimens. 

 3 d. An individual, still preserving its natural proportions. 



3 e, /, g. Profile views of three specimens, showing the variable elevation of the beak of the dorsal valve, 



and width of the area. 

 3 h, i. Front views of specimens, showing a different proportional convexity. 



3 ft. A portion of the surface enlarged. 



Fig. 4. 624. 7. Spirifer bicostatus. ( Pag. 263.) 



4 a. A dorsal valve of an individual of this species. 



4 b. Ventral view of the same, showing the area and foramen, the beak of the ventral valve being broken oflF. 

 4 c. Profile view, showing the form of the dorsal valve. 

 • 4 <f. Front view, in which the elevation of the ventral valve is given as it appears to have been in its perfect 



state. 



4 e. An enlarged portion of the surface, showing the character of the stria. 



Fig. 5. 625. 8. Spirifer niagarensis. ( Pag. 264.) 



5 a, b. Ventral and dorsal views of a young specimen. 5 c. Front view of the same. 

 5 d. Profile view of another more gibbous specimen. 



5 e, /, g. Ventral, front and profile views of a well preserved specimen. 



5 h, i. Ventral and profile views of a well preserved specimen of the ordinary size of this species. 



5 fc. A flattened dorsal valve of about the same size as the preceding specimen. 



•5 I. A flattened ventral valve of a specimen somewhat larger than the preceding. 



5 m. A large specimen, having the form well preserved. 5 n. Front view of the specimen tig 5 h. 



5 o. Cardinal view of a small specimen, where the area is nearly closed. "^ 



b p. Cardinal view of a specimen where the lower part of the shell is compressed. 



5 r. The interior of a dorsal valve, showing the strong lamelte on each side of the triangular foramen. 



5 s. An enlargement of the stria3. 



5 t. Section of the plications, showing their form and the number of striee upon the surface. 



Fig. 6. 452. 3. Spirifer radiatus. (Pag. 265.) 



6 a, b. Ventral and front view of a small specimen. 



6 c. A large specimen entirely flattened, which causes the beak to project as shown in the figure. 

 Q d. A specimen from which the shell is partially exfoliated, showing the form of the muscular impression. 

 6 e. Cardinal view of the same, showing the entire extent of the dorsal area and foramen. 

 6 /. The interior of a dorsal valve, showing the extension of the plates or laminae on each side of the for.v 

 men, with a central one commencing below the beak. 6 g. Several of the striae enlarged. 



6 h. Transverse section showing comparative elevation and width of striae. 



Fig. 7. 626. 9. Spirifer pyramidalis. (Pag. 266.) 



7 a. The ventral valve of this species. 7 b. Dorsal valve of the same. 

 7 c. Cardinal view, showing the area and long linear foramen which is closed. 

 7 d. Profile view of the same. 



7 e. Several of the plications enlarged, showing the concentric striae. 



