Parazyca Drweyy, Hall. 
Figs. 17. 18. Dorsal and profile views of the original specimen. 
Fig. 19. A preparation showing the form of the jugum and mode of attachment 
of the primary lamelle and crura. 
Fig. 20. A portion of the brachial valve; showing the form of the hinge-plate. 
Lower Helderberg group. The Helderbergs, N. Y. 
NUCLEOSPIRA, Hatt, 
Page 806. 
Nouctizospima Pisum, Sowerby. 
Fig. 21. A dorsal view; showing the fine surface spinules. 2. 
Wenlock shale. England. 
Novctrospira veNntTRIcosA, Hall. 
Fig. 22. A dorsal view of a shell retaining the epidermal spinules over a portion 
of its surface. >» 2. 
Fig. 28. Profile view of a comparatively large individual denuded of its spines. 
Fig. 24. The interior of the brachial valve. with a portion of the pedicle-valve 
adhering, viewed from in front; showing the elevation and lobation 
of the hinge-plate, and the median septum. x 2. 
Fig. 25. A profile of the brachial valve; showing the recurved hinge-plate. 
Fig. 26. A preparation showing the broad umbonal blades of the primary 
lamellz, their attachment to the crura, and also the lateral branches 
of the jugum, the upright stem being broken off. »38. 
NucLEosPirA ELEGANS, Hall. 
Figs. 27, 28. Dorsal and profile views of a normal specimen. 
Lower Helderberg group. Cherry Valley, N. Y. 
Fig. 29. A preparation exposing, by the removal of the pedicle-valve, the 
structure of the brachidium, At (/) is the projecting upright stem 
of the jugum. 
Lower Helderberg group. Schoharie, N. Y. 
Nuc.Lrospira concinna, Hall. 
Fig. 30. A dorsal view of an average specimen retaining in part the surfacespines. 
Fig. 31. A cardinal view of conjoined valves. 
Fig. 32. An internal cast of the pedicle-valve; showing the adductor and 
diductor scars. % 2. 
Fig. 38. An enlargement of the cardinal portion of the pedicle-valve; showing 
the concave and coalesced deltaria. x 5. 
Fig. 34. Profile view of conjoined valves. 
Fig. 35. Profile view of the brachial valve; showing the projection of the 
hinge-plate. 
Hamilton group. Western New York. 
Fig. 36. A view of the hinge-plate ; showing its concave surface and strong 
crural lobes. x 3. 
Fig. 37. The same specimen viewed from in front; showing the elevation of 
the plate. 
Corniferous limestone. Colwmbus, Ohio. 
Fig. 38. The interior of the brachial valve ; showing the hinge-plate and 
adductor scars. X 2. 
Hamilton group. alls of the Ohio. 
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