PLATE XXV—Continued. 
Genus CTliTIA, Dalman. 
Page 40. 
Cyrtia cyrtiniformis, Hall and Whitfield. 
Fig’S. 26-28. Three views of a normal example ; showing the external characters. 
Fig. 29. A cardinal view ; showing the great height of the area. X 2. 
Fig. 30. The central cai-dinal portion of the conjoined valves; showing the dental plates of the pedicle- 
valve, the cardinal process and socket-walls of the brachial valve. X 2. 
Fig. 31. The interior of a portion of the brachial valve; showing the cardinal process, dental sockets and 
socket-walls, and the subdivision of the muscular area. X 3. 
Fig. 32. A specimen, showing the crura, jugal pi'ocesses and spiral cones. 
Hamilton group. Rockford, Iowa. 
Genus SYEINGOTHYRIS, A. Winchell. 
Page 47. 
Syringothyris Hannibalensis, Swallow. 
Fig. 33. The exterior of a portion of the brachial valve. 
Fig. 34. A cai'dinal view of the pedicle-valve ; showing the delthyi'ial callosity or canaliferous j)late. 
Fig. 35. The articulating apparatus of the brachial valve. X 2. 
Choteau limestone. Pike county, Missowi. 
