Fig. 9. Cardinal view of the specimen represented in figure 7; showing the 
cardinal area. 
Fig. 10. A portion of the interior of the pedicle-valve; showing the complete 
spondylium and the division of its surface into median (adductor) 
and lateral (diductor) muscular areas. 3. 
Fig. 11. Cardinal view of conjoined valves which have been transversely sec- 
tioned in the umbonal region; showing the spondylium in both 
valves. The shell has been cut just in front of the supporting septa, 
the brachial valve being above. <2. ~ 
Fig. 12. Oblique view of the specimen represented in figure 10; showing the 
elevation of the spondylium and the length of its supporting median 
septum. 
Calciferous formation (Fort Cassin beds). Fort Cassin, Vermont. 
CAMARELLA, Brxzives. 
Page 838. 
CamarELLta Voxzorrat, Billings. 
Figs. 18, 14, 15. Dorsal, ventral and profile views of a strongly plicated 
shell. X 2. 
Fig. 16. The interior of the umbonal portion of the brachial valve; showing 
the small apical spondylium and the median septum. ~* 4. 
Fig. 17. Cardinal view of conjoined valves which have been transversely sec- 
tioned in the umbonal region; showing the spondylium of the 
pedicle-valvé and its median supporting septum. * 4. 
Black River limestone. Pauquette’s Rapids, Ottawa River. 
(Attention is directed to the fact that figures 18 and 19 do not belong with 
the genus CAMARELLA but should have been included within the lines enclosing 
figures of the following genus, PARASTROPHIA.) 
PARASTROPHIA, Hatt. 
Page 839. 
PaRASTROPHIA REVERSA, Billings. 
Fig. 18. Dorsal view of a specimen; showing the fine concentric lineation of 
the surface, 
Fig. 19. Cardinal view of the exterior of an average example; showing the 
relative convexity of the valves and the character of their plication. 
Fig. 23. Cardinal view of a specimen which has been transversely sectioned in 
the umbonal region, the brachial valve being represented below; 
showing the spondylium of the pedicle-valve supported by its median 
septum, and the septal plates of the brachial valve resting on the 
‘bottom of the shell and supporting the crural apophyses. 
Clinton horizon. Island of Anticosti. 
PARASTROPHIA HEMIPLICATA, Hall. 
Figs. 20, 21. Dorsal and front views of an average specimen; showing the 
elevation of the plicated fold. ; 
247 
