PLATE 9. 
Page 
Figs. 1 - 12. Streptorhynchus chemungensis var. arctostrtata. 71 
I, 2. Ventral valves of young specimens where the beaks are somewhat distorted, and the strias 
not alternating in strength. 
3, 4. External and internal views, of a dorsal valve of similar character. 
5. Interior of a dorsal valve, the striae of which are sharp and equal in size. 
6, 7. Exterior and interior of a larger dorsal valve, the striae of which are distinctly alternating 
in strength. 
8, 9. Ventral and dorsal valves of a semicircular form, where the striae are sharp and of equal 
strength. Original of Orthisina [S.l arctostriata, 13th Report on State Cabinet. 
10. Cardinal view of specimen, fig. 2, showing the distortion of the beak and the covered fora¬ 
men ; enlarged to two diameters. 
II. Interior of a ventral valve of a specimen having equal striae; showing muscular impression, 
teeth and covered deltidium.' 
12. Enlarged view of a cast of a specimen having sharp equal striae, and showing the imprint of 
the adductor and retractor muscles very well preserved. 
12. t Enlargement of surface striae, showing their alternating character. 
Figs. 13-17,26. Streptorhynchus chemtjngensis var, perversa. 72 
13, 14. Dorsal valves of specimens, showing the alternating character of the striae. 
15. View of an imperfect ventral valve. 
16. Ventral valve of an individual retaining but a portion of the shell. 
17. Cast of a large dorsal valve showing the impression of the alternating striae. 
26. View of a very convex finely striated dorsal valve; referred with doubt to S. perversa. 
Figs. 18-25, 27. Streptorhynchus chemungensis var. pandora. 68 
18,19, 20. Dorsal and ventral views and profile of a very symmetrical specimen of the species. 
21. Interior of a dorsal valve, showing the muscular impressions, cardinal process and socket 
plates. 
23. Interior of a ventral valve, showing muscular impressions, cardinal area and teeth. 
24, 25. Casts of a dorsal and ventral valve, showing the characters of the muscular impressions. 
27. Exterior of a large ventral valve. 
