Fig. 22. Cardinal view of an internal cast; showing the median septa and 
spondylia of both valves. 
Trenton limestone. Jacksonburgh, N. Y. 
PARASTROPHIA LaTIPLICATA, Hall. 
Fig. 24. An internal cast of the brachial valve in which the filling of the spon- 
dylium is exposed and the four scars of the adductor impression 
distinctly retained. 
Fig. 25. Cardinal view of the same specimen. 
Niagara dolomites. Near Milwaukee, Wisconsin. 
PARASTROPHIA MULTIPLICATA, Hall. 
Fig. 26. Cardinal view of an individual, showing the casts of the spondylia of 
the two valves, in the brachial valve the lateral walls having rested 
upon the inner surface of the shell. The muscular scars of the 
brachial valve are also retained. 
Niagara dolomites. Near Milwaukee, Wisconsin. 
ParasTRoPHIA GREENI, Hall. 
Fig. 27. Cardinal view of a rather convex internal cast; showing the cavities 
left by the median septa. 
Niagara dolomites. Near Milwaukee, Wisconsin. 
ANASTROPHIA, Hatt. 
Page 839. 
Awnastropaia VERNEUILI, Hall. 
Figs. 28, 29. Dorsal and front views of an average specimen with regularly and 
sharply plicated surface. 
Fig. 30. Cardinal view of a large individual; showing the contour and 
character of surface plication. 
Fig. 31. An interior with the septal plates and muscular scars sharply defined; 
showing also the false foramen produced by the encroachment of the 
septal cavity or spondylium upon the beak. 
Fig. 32. An enlargement of the interior of the umbonal region of conjoined 
valves, the pedicle-valve being represented below. In the brachial 
valve the convergent septal plates bear lateral bilobed expansions or 
flanges, which are the crural apophyses asshown in section, in fig. 33. 
In the pedicle-valve the walls of the supported spondylium are 
folded overeach other in such a manner as to form a tubular chamber. 
This appears to be an abnormal character, as it has been observed in 
this instance only, but it is nevertheless a natural growth without 
evidence of break or lesion in the walls of the spondylium, * 2. 
Lower Helderberg group. The Helderbergs, N. Y. 
Fig. 35. Cardinal view of an internal cast, represented with the brachial valve 
above; showing the cavities of the septal and socket plates in the 
brachial valve, and of the spondylium and its median septum in the 
pedicle-valve. * 2. 
Niagara dolomites. Near Milwaukee, Wisconsin. 
248 
