PLATE 96. 



PugO 



Fig. 1-6. Cyrtia bostrata. 429 



\ a, b. Dorsal and cardinal views of a young specimen, which has six plications on each side 

 of the mesial fold. 



2 a, b. Dorsal and front views of a larger specimen. 



2 c, d. Profile and cardinal visws of the same specimen. 



3 a, b. Cardinal and front views of another individual, with a higher area and less extended 



hinge-line. The beak in fig. 3 a, as represented, is not sutljciently elevated. 



4 a, b. A'entral and dorsal valve of an old specimen. 



4 c, d. Profile and cardinal views of the same specimen. 



6. Interior of the dorsal valve. 



6 a, b. The exterior and interior of a dorsal valve of this species. 



Fig. 1 a -f. Spirifer submucuonatus. 419 



7 a, b. Ventral and dorsal views of a specimen of this species. 

 7 c. A specimen with one of the cardinal angles more extended. 

 7 d. Front view of the preceding. 

 7 e. Profile view of a specimen of this species. 



7 /. The interior of the ventral valve. 



Fig. % a - e. Spirifer tribulis. 420 



8 a, b. Ventral and dorsal views of a specimen of ordinary size. 

 8 c. Front view of a specimen which is less gibbous than usual. 



8 d. Profile view of a more gibbous specimen. ( The dorsal valve is represented as too convex.) 

 8 «. An enlargement of the surface, showing the tine concentric and radiating striiB. 



Fig. 9 a - k. Spirifer cumberlandi^. 421 



9 a, 6. Dorsal and ventral views of a large individual, showing the foramen almost entirely 



closed. 

 9 c. Front view of another individual. v 



9 d. Profile view of the .specimen. 



9 e. Ventral view of a specimen from the upper part of which the shell is removed, showing 

 the cast of the muscular area and the rostral cavity. 



9/. Interior of the dorsal valve, showing the cardinal and crural processes, with the dental 

 fossets, 



9 g. Interior of the ventral valve, showing the partial closing of the foramen, with a perfora- 

 tion at the summit, the dental lamella;, etc. 



9 h. View of a cast of the internal spiral appendage, probably of this species. 



