PLATE LXXIII—Continued. 
Genus AMPHIGENIA, Hall. 
Page 252. 
See Plate 74. 
Amphigenia elongata, Vamixem. 
Fig. 
16. 
Fig. 
17. 
Fig. 
18. 
Fig. 
19. 
Fig. 
20. 
Ventral view of a cast of the interior of the pedicle-valve ; showing the tilling of the spondylium 
and the cavity of the short median septum. 
Schoharie grit. Schoharie, Neio Yor'k. 
The interior of the umbonal portion of a brachial valve; showing the structure of the hinge- 
plate, its apical perfoi’ation, and the crura with their jugal processes. 
Profile view of the same .specimen somewhat enlarged to show the direction and extent of the 
crui-a, jugal apophyses and crural plates. 
The interior of the umbonal portion of the pedicle-valve; showing the teeth and the entire spon¬ 
dylium. 
Corniferous limestone. Le Roy, New Ym'k. 
The interior of the umbonal portion of a pedicle-valve; showing vascular sinuses on the surface 
of the valve beneath the spondylium. 
Corniferous limestone. Prom the (R-ift of Southern Michigan. 
