PLATE 54. 



Fig. 1. 621. 4. SriRiFF.u dilohus. (Pag- 260.) 



1 a. b. Vfiitral ami dorsal view, wliorc the fxtri'iiiitics of tlio liiiigo-liiie are scarcely cxteudcd. 

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

 1 e. Front view of a speeimen, showing the bilobate eliaraeter. • 



1 /, g. Profile views of two spei-imens, one of which is much more convex than the other. 

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



1 k. Interior of the ventral valve. 



Fig. 2. 622. 5. SriRiFER 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 info mueronate points. 



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



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



2 f. Front view of lig. 2 b. 2 g. Front view of 2 e. 



2 ft, I. Profile views of ditFerent specimens. 



2 k. An cnlargemeut of the surface, showing the longitudinal strise crossing the lamellae. 



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



3 a, 6, c. Ventr.ll views, presenting the 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 A, t. 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 dor.sal 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 ofT. 

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



4 d. 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 strise. 



Fig. 5. 625. 8. Spirifer niagarensis. ( Pag. 2C-1.) 



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



6 d. Profile view of another more gibbous specimen. 



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



5 A, »'. Ventral and profile views of a well preserved specimen of the ordinary size of this sjieeies. 



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



5 /. A flattened ventral valve of a specimen somewhat larger than tlie preceding. 



5 m. A large spee'men, having the form well preserved. -5 n. Front view of the specimen fig 5 h. 



5 0. Cardinal view of a small specimen, where the area is nearly closed. 



6 J). Cardinal view of a specimen where the lower part of the shell is compressed. 



6 1-. The interior of a dorsal valve, showing the strong lamelUe on each side of the triangular foramen. 

 5 «. An enlargement of the stria>. 



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



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



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



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



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

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



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



men, with a central one commencing below the beak. G g. Several of the .stria> enlarged. 



h. Transverse section showing comparative elevation and width of stria;. 



Fig. 7. 626. 9. Spirifer pyramidalis. ( Pag. 2G6.) 



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 stria-. 



