PLATE 38. 
Legend: t. Teeth. hp. Hinge-plate. 
dp. Deltaria. 1. Stem of jugum. 
c. Crura. ub. Umbonal blades. 
c’. Lateral divisions of hinge-plate. a. Adductor scars. 
dt. Foraminal sheath. r. Diductor scars. 
TREMATOSPIRA, Hatt. 
Page 798. 
TREMATOSPIRA CAMURA, Hall. 
Fig. 1. Ventral view of a rather large specimen. 
Fig. 2. Ventral view of a preparation showing by translucence the structure 
of the brachidium. *X 3. 
Niagara group. Lockport, N. Y. 
TREMATOSPIRA MULTISTRIATA, Hall. 
Figs. 3, 4. Dorsal and ventral views of a normal example. 
Fig. 5. A preparation showing one of the spiral cones, the form of the jugum 
and the mode of attachment of primary lamellz and crura. 
Fig. 6. The central cardinal portion of the pedicle-valve, viewed from the 
apex; showing the foramen, teeth and concave, coalesced deltaria. 
Fig. 7. A similar portion of the brachial valve; showing the elevation of the 
divisions of the hinge-plate, the formation of a small median cal- 
losity, the constriction at its base and the striated basal callosity. 3. 
Fig. 8. Another view of the hinge-plate; showing its deep median excava- 
tion. X 3. 
Lower Helderberg group. The Helderbergs, N. Y. 
TrEmatospira Hippotyte, Billings. 
Fig. 9. Dorsal view of the original example. 
Lower Helderberg group. Square Lake, Maine. 
TREMATOSPIRA SIMPLEX, Hall. 
Fig. 10. Dorsal view of anormalexample. ~* 2. 
Fig. 11. Anenlargement of thesurface; showing the pustules of the outer lamin. 
Lower Helderberg group. Decatur county, Tennessee. 
TREMATOSPIRA CosTATA, Hall. 
Fig. 12. Dorsal view of a large example. 
Lower Helderberg group. The Helderbergs, N. Y, 
PARAZYGA, Hatt. 
Page 800. 
PaRAZYGA HIRSUTA, Hall. 
Fig. 13. Dorsal view of a normal shell, deprived of its surface spinules. 
Fig. 14. The interior of the pedicle-valve; showing the muscular area. 
Fig. 15. The interior of the brachial valve; showing the hinge-plate. 
Fig. 16. The interior of the rostral region of the pedicle-valve; showing the 
pedicle-sheath. X 3. 
Hamilton group. Western New York. 
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