40 
Fig. 1. 
BULLETIN OF THE 
EXPLANATION OF PLATES. 
PLATE I, 
‘ 
Obolella crassa, Hall, var.; a, dorsal valve; 6, interior cast of the same, 
the features of the central area exaggerated to explain theoretical views; c, the 
same, in its normal state; d, the interior surface of the dorsal valve diagrammati- 
cally represented; e, the interior cast of the ventral valve; /, the interior surface 
of the ventral valve diagrammatically represented. 
In the diagrammatic figures: x, cardinal area; a, cardinal muscles; d, lateral 
muscular scars; c, central muscular scars; p, a notch in the cardinal area. 
Fig. 2. 
Obolella ; a, ventral valve ; b, interior surface of the same; c, a diagram- 
matic representation of the same. 
Fig. 3. 
Fig. 4 
Fig. 5 
Fig. 6. 
Fig. 7 
Fig. 8 
Fig. 9 
men. 
Fig. 10. 
Probably a cast of an operculum of some species of Hyolithes. 
. Fordilla Troyensis, Barrande ? 
. Lamellibranch 2 
Scenella reticulata, Billings; a, lateral view ; b, outline of base. 
. Stenotheca rugosa, var. pauper. 
. Stenotheca curvirostra, sp. n. 
. Stenotheca rugosa, var. abrupta; a, normal type; », a single larger speci- 
Platyceras primevum, Billings ; a, seen from above; b, an umbilical view 
of the same, specimen laterally compressed. 
Fig. 10. 
Fig. 11. 
Fig. 12. 
Fig. 13. 
Fig. 14. 
Fig. 15. 
PLATE II. 
Platyceras primevum, Billings ; c, a specimen of normal type. 
Pleurotomaria (Raphistoma) Attleborensis, sp. n. 
Paradoxides Walcotti, sp. n. 
Miscrodiscus lobatus, Hall. 
Ptychoparia Attleborensis, sp. n. ‘ 
Hyolithes quadricostatus, sp. n. Ventral view; a section near its larger 
extremity, and a basal view of the septum. 
Fig. 16. 
Hyolithes Americanus, Billings ; ventral view, and cross-section near its 
larger extremity. 
Fig. 17. 
Hypolithes communis, var. Emmonsi, Ford; dorsal view, with cross-section 
of its larger extremity, and basal view of the septum. 
Fig. 18. 
Fig. 19. 
Aristozoé ? 
Microdiscus belli-marginatus, sp. n.; a, head; b, pygidium. 
