482 
PALAEONTOLOGY OF NEW-YORK. 
8tropho<lonta intermedia (n. s.). 
Plate XCV A. Fig. 13 & 14. 
Shell semioval. Dorsal valve depressed-convex : hinge-line equalling the 
greatest width of the shell; cardinal process duplicate, each branch 
deeply grooved on the rostral side ; lamellm thin and curving, and 
leaving between them and the hinge-line deep pits for the reception of 
the dental lamellae ; muscular impressions somewhat broadly flabelli- 
form, and divided by a short low mesial septum. 
Surface marked by fine rounded radiating striae, which are increased by 
the interstitial addition of very slender sharp striae at intervals be¬ 
tween the beak and margin of the shell. Many of the striae curve 
upwards, and run out upon the hinge-line. 
Fig. 13. The exterior of the dorsal valve. 
Fig. 14. The interior of the same. 
Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 
Strophoilonta magnifica. 
Plate XCY A. Fig. 15 - 19. 
For description and references, see pages 414 and 415. 
Fig. 15. A dorsal view, showing the area, which is imperforate and striate. The specimen is 
below the medium size which this shell usually attains. 
Fig. 16. Ventral view of the same : the margins are broken, and the outline is consequently 
imperfect. 
Fig. 17. The interior of a ventral valve of the same species, showing a central pit or foramen. 
Fig. 18. View of the area when the linear foramen is closed. 
Fig. 19. Enlargement of the striae, showing their mode of bifurcation, and the puncta which 
are very regularly interposed between the striae. 
