PLATE XLVIII. 
(Figs. 1-3, 6,10,11, 21-24, 26-29, 33, 34 by E. Emmon.s; 4, 5,„7-9 by F. B. Meek; 12-20, 25, 30-32 by R. P. Whitfield.) 
Legend: D. Coalesced deltidial plates, 
t. Teeth. 
s. Median septum, 
a. Adductors, 
a'. Anterior adductors. 
r. Deductors. 
c. Crura, 
hp. Hinge-plate, 
uf). Umbonal blades. 
1. Stem of loop. 
Genus NUOLEOSPIKA, Hall. 
Page 142. 
Nucleospira pisum, Sowerby. 
Fig. 1. A dorsal view; showing the fine surface spines. X 2. 
Wenlock shale. England. 
Nucleospira ventricosa, Hall. 
Fig. 2. A dorsal view of conjoined valves which retain the epidermal spines over a portion of the surface. 
X 2. 
Fig. 3. A profile view of a comparatively large individual, denuded of its spines ; showing the usual con¬ 
vexity of the valves. 
Fig. 4. A profile view of a brachial valve ; showing the ci'ural bases and the recurved hinge-plate 
extending backward beyond the apex of the valve. 
Fig. 5. The interior of a brachial valve with the umbonal portion of the pedicle-valve adhering, view'ed 
from in front; showing the elevation and lobation of the hinge-plate, and the median septum. 
Fig. 6. A prejiaration, showing the broad umbonal blades of the primary lamellse, their attachment to the 
crura, and also the lateral branches of the loop, the upright stem being broken off. X 3. 
Fig. 18. The interior of a pedicle-valve ; showing the concave coalesced deltidial plates and the median 
septum. 
Lower Helderberg grouji (Shaly limestone). The Helderhergs, N. Y. 
Nucleospira concentrica, Hall. 
Fig. 7. The exterior of a pedicle-valve ; showing the sharp concentric growth-lines. 
Lower Helderberg group. Decatur county, Tennessee. 
Nucleospira elegans, Hall. 
Fig. 8. A dorsal view of conjoined valves ; showing the transverse form of the shell and the low median 
sinus on the brachial valve. 
Fig. 9. A profile view of the same specimen. 
Lower Helderberg group. Cherry Valley, N. Y. 
Fig. 10. A preparation exposing, by the partial removal of the pedicle-valve, the sti-ucture of the brachi- 
dium. In the umbonal region the crura and umbonal blades are exposed, and at {1) is the 
projecting upright stem of the loop. All of the lamellie are slightly encrusted with a silicious 
deposit. X 2. 
Fig. 11. A profile of the same specimen; showing one of the cones and the projecting extremity of the 
loop. X 2. (c.) 
Lower Helderberg group (Shaly limestone). Schoharie, N. Y. 
Nucleospira concinna, Hall. 
Fig. 12. A dorsal view of conjoined valves retaining a portion of the spinulose surface. 
Figs. 13-16. Ventral, dorsal, cardinal and profile views of a normal example from which the surface spinules 
have been lost; showing the normal subplano-convex contour of the valves and the linear 
median depression on each. 
Fig. 17. The interior of a pedicle-valve ; showing the concave, coalesced deltidial plates, articulating pro¬ 
cesses, adductor and diductor scars. 
