PLATE 22. 



Fig. 1. _ 172. 1. Spirifer biforatus, t!ar. lynx. ( Pag. 65.) 



1 a. Ventral valve, with a very short hingc-linc. There are four mesial plates, and twelve or thirteen on each 



side. 

 1 b. The ventral valve of another specimen, having the mesial lobe worn smooth, and ten ribs on eaeb side. 

 1 c. The dorsal valve of a large specimen, having four rilw in the mesial sinus, and ten on each side. 

 1 d. The interior of the dorsiil valve, showing the ftrm of the muscular impression, and the papillose surface 



on each side. 



1 €. Cardinal view of the ventral valve, showing the projecting dental processes. 



Fig. 2. 452. 3. Spirifer radiatus. (Pag. 66.) 



2 a. Ventral view of a si)ecinien having the cardinal extremities somewhat contracted, and the dorsal area 



very wide and fully exposed. 



2 b. Profile view of the same. 



2 c. A specimen with the dor.sal extremities more extended, and the area broad. 



2 d. An individual much extended in width, having the cardinal extremities rounded and the area almost 

 closed. 2 c. A similar specimen, larger than the last. 



2/. A specimen with the lunge-line very much contracted and the angles rounded, with the area nearly 

 closed. 



2/ t. A portion of the surface enlarged, showing the character of the strias. 



2 f . A specimen which has apparently suffered no pressure. The beaks are approximate, the dorsal one 

 much curved, and the area nearly closed. The cardinal extremities arc rounded, and the whole con- 

 tour of the shell very round. 2 h. Profile view of the last. 



2 i. Front view of the same, showing the elevation of the mesial lobe. 



2 k. Ventral view of a larger specimen with the cardinal extremities rounded, the beak much elevated and 

 incurved, and the area very small. 2 /. Profile view of the last. 



2 m. Dorsal view of the same. 2 n. Front view of the same. 



2 0. Dorsal view of a larger specimen, having the extremities rounded, and the beak much elevated and in- 

 curved. 



ip. Veutr.ll view of the same, showing the area nearly closed. 



2 r. Cardin.ll view of the same shell. 



2 s. Dorsal view of a specimen with the shell partially exfoliated, showing the direction of the dental plates. 



2 t. Dorsal area of a single valve, showing the narrow foramen. 



Fig. 3. 4-51. 2. Spirifer . (Pag, 66.) 



