Figs. 1 -12. 
PLATE 50. 
MERISTELLA DORIS. 
Pago 
BUB 
1. A dorsal view of a small specimen, from the Schoharie grit. 
2. A dorsal view of a small individual. This, and the following figures, are of specimens from 
the Corniferous limestone. 
3. 4. Dorsal and ventral views of an unsymmetrical specimen, of medium size. 
5, 6. Dorsal and profile views of a specimen of medium size and perfect form. 
7. "Ventral view of a large individual, which is somewhat imperfect at the beak. 
8-10. Dorsal, profile and front views of a large individual. 
11. The dorsal valve of a large individual. 
12. Cardinal view of a cast, showing the muscular impressions and the cavities made by the 
* removal of the dental lamellae and median septum. 
Figs. 13-17. Meristella rostrata.. 307 
13-16. Dorsal, ventral, profile and front views of a specimen. 
17. Dorsal view of a specimen, having a somewhat different form from the above. 
Figs. 18-35. Meristella (Pentagonia) unisulcata. 309 
18-20. Dorsal, ventral and cardinal views of a small specimen, presenting the ordinary charac¬ 
ters of the species. 
21. Dorsal view of a small individual, having a less extended hinge line, giving the shell a more 
triangular form. 
22, 23. Dorsal and ventral views of a specimen of medium size. 
24. A cardinal view of a somewhat larger individual, showing a deep sinus in the mesial fold. 
25-29. Dorsal, ventral, front, cardinal and profile views of a large but not very gibbous specimen. 
30-32 Ventral, front and cardinal views of a narrow gibbous form, from the Falls of the Ohio. 
33, 34. Interiors of the dorsal and ventral valves, showing the hinge structure and muscular im¬ 
pressions. From the Falls of the Ohio, communicated by Major S. S. Lypn. 
35. A cardinal view of a specimen, from the Hamilton shales of New York, showing a second 
fold on the cardinal margin of the dorsal valve. 
