PLATE XXI. 
(Figures 1-29 by It. P. Whitfield.) 
Leg’eiid ; 
A. Delthyriuin. 
D. Deltidimn. 
t. Teeth, 
d. Dental plates, 
j. Cardinal pi'ocess 
b. Dental sockets. 
c. Crura. 
s. Median septum. 
s'. Callosity in the delthyriuin. 
X. Crural ridges, 
r. Diductor scars. 
Genus SPI LIFER, Sowerhy. 
Page 1. 
Spirieer Niagarensis, Connid. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
1. A medium sized sjiecimen ; showing the radiate-lineate exterior. 
2. The interior of the cardinal portion of a brachial valve ; showing the crural plates. 
3. A jiortion of the interior of the pedicle-valve; showing the elongate muscular area. 
4. The median portion of the cardinal areas of conjoined valves; showing the deltidium, cardinal 
process and crural plates. X 3. 
25. The surface characters. X 5. 
Niagara group. Lockport, N. Y. 
Spirieer plicateleus, Limie. 
Figs. 6-8. Figures of typical specimens of this form ; the first from Sweden, the other from the Island of 
Gotland. Figure 28 is an enlargement of the surface of the latter. 
Spirieer radiates, Sowerby. 
Fig. 5. A small individual with a few low lateral plications. This is, apparently, one of the passage forms 
between the typical S. plicatelhis and the non-plicate iS. radiatus. Distinction between the two 
forms is not jiossible among American shells. 
Niagara group. Locality 9 
Fig. 9. A partial cast of the interior ; showing the diductor scars. 
Fig. 10. A cardinal view of a sjiecimen partially retaining the deltidium. , 
Niagara group. Western New York. 
Fig. 11. A typical non-plicate adult retaining the deltidium. 
Fig. 12. The interior of the pedicle-valve ; showing teeth and muscular scars. 
Fig. 13. The interior of the cardinal portion of the brachial valve ; showing the dental sockets and crural 
plates. 
Fig. 26. An enlargement of the surface characters. 
Niagara group. Waldron, Indiana. 
Spirieer radiates, Sowerby (?). 
Figs. 16, 16. Opposite sides of an internal cast of both valves ; showing the elevated cardinal area, and im¬ 
pressions of the long dental plates in figure 16. 
Figs. 17, 18. Two views of a larger internal cast; showing the elevated area, and faint median ridge on the 
brachial valve. 
Fig. 14. The interior of a portion of the conjoined valves ; showing a low median septum in the brachial 
valve. ' 
Niagara dolomites. Wisconsin. 
This shell is nan ower on the lateral slopes than the more typical forms of iS. radiatus, and differs 
from them intei'nally in the presence of the slight median septum in the brachial valve. 
