PLATE LXXVI—Continued. 
visceral canal, the outer opening' being' visible at the apex of the plate. This canal is, how- 
e'ver, closed by testaceous deposit, and the median division of the plate on its upper surface 
largely obscured from the same cause. 
Fig. 20. The interior of the umbonal portion of the pedicle-valve ; showing the dental plates and muscular 
impressions. 
Oriskany sandstone. Omnberland, Maryland. 
Genus AMPHIGENIA, Hall. 
Page 25-2. 
Amphigenia elongata, Hull. 
See Plates 73, 74. 
Fig. 9. The cardinal portion of the brachial valve ; showing the form of the hinge-plate, its median 
depression, the opening of the visceral foramen, a portion of the septal plates and the branch¬ 
ing vascular sinuses. 
Corniferous limestone. Le Hoy, JS'ew Yoi'k. 
Genus RENSSELH2RIA, Hall. 
Page 2.54. 
Renssel^kia ovoides, Eaton. 
See Plate 75. 
Fig. 16. The hinge-plate enlarged; showing its foi-m, the opening of the visceral canal, the highly 
- developed crural plates ; also the elongate dental sockets and outer socket walls. X 2. 
Fig. 18. A cast of the hinge-plate ; showing the unbroken tilling of the visceral canal. 
Oriskany sandstone. The Helderhergs, New Ym'k. 
Renssel^eria mutabilis, Hull. 
See tigures l-3a. 
Figs. 21, 22. Dorsal and profile views of a broad, ovate form with elevated umbo, open delthyrium, well- 
defined cardinal slopes and rather coarse surface plication. 
Lower Helderberg group. Becraft’s Mountain, Columbia county. New Ywk. 
ReNSSELA!1RIA iEQUIRADIATA, Coiliud. 
Figs. 23, 24, 25, Dorsal, profile and front views of one of the original specimens ; showing the form of the 
shell and the character of its plication. 
Lower Helderberg group (Upper Pentamerus limestone). Schoharie, New Yoi'k. 
RENSSELiERIA ELLIPTICA, Hull. 
Figs. 26, 27, 28. Dorsal, profile and front views of the original specimen; sho5ving the form and convexity 
of the shell. 
Lower Helderberg group (Shaly limestone). SchohaHe, New Yoi'k. 
