PI.ATK LXXIIl— ContinaeU. 



Genus AMPHIGENIA, Hall. 



Page 25-i. 

 See Plate 74. 



Amphigenia elongata, Vauuxein. 



Pig. 16. Ventral view of a ca.st of the interior of the pedicle-valve ; Hhowing the tilling- of the spondylium 

 and the cavity of the sliort median septum. 



Schoiiarie grit. iSchoharie, New York. 

 Fig. 17. The interior of the umboual portion of a brachial valve; showing the .'structure of the hinge- 

 plate, its apical jjerforation, and the crura with their jugal processes. 

 Fig. 18. Proiile view of the same .sjiecimen somewhat enlargeil to show the direction and extent of the 



ci'ura, jugal apophyses and crural plates. 

 Fig. 19. The interior of the umbonal portion of the pedicle-valve ; showing the teeth and the entiie spon- 

 dylium. 



Corniferous limestone. Le Roy, New York. 

 Fig. 20. The interior of the umbonal portion of a pedicle-valve ; showing vascular sinuses on the surface 

 of the valve beneath the spondylium. 



Coi-niferous limestone. P)-om the drift of Southern Michigan. 



