PLATE XXXIX— Continued. 



Gknus CYETINA, Davidson. 



Page 43. 



See Plates 25, 28. 



Cyktina, «p. ? 



Fig. 2!). An enlargement of the .siirfiice ; showing the bases of concentric rows of spinules. X 4. 



Fig. 26. Caidinal view of an internal east of tli<! pedicle- valve, broken so as to sliow the convergent dental 



plates uniting with the median septum, and the slight projection of the edge of the latter within 



the siiondyliuni thus formed. 

 Fig. 27. The saini; siiecinien viewed fi'om at)0ve ; showing the length of the median septum. 

 Fig. 28. An enlai'gement of a poition of the interior of the ))edicle-valve ; showing the convergence of the 



dental plates, and the projection of the median septum tieyond their union. X 3. 

 Chert-beds of the Burlington limestone. Burlingtmi, lovM. 



Genus SYRINGOTPIYRIS, Winchell. 



rage 47. 

 See Plates 25, 26, 27. 



Syringothvkis Missouri, .sp. iiov. 



Figs. 29-31. Three views of the typical specimen ; showing its small size, elevated pedicle-valve, broadly 

 rounded cardinal margin.s, and coarse lateral plications. Internally this shell has the syringo- 

 thyroid tubifei'ons plate, and the shell-substance is highly punctate. 

 Choteau limestone. Pike county, Missouri. 



Genus CYRTIA, Dalman. 



Page 40. 



See Plates 21, 25, 26, 28. 



Cyriia e.xporrecta, VViihlenl)eig, v:ir. akrecta, Hall and \\'liilliclil. 



See Plate 28. 

 Fig. 32. View of the umboiial cavity of the conjoined valves ; showing the foramen, the strong dental 

 plates, and the articulating apparatus. X 2. 



Ni.agai-a group. Louisxnlle, Kentucky. 



Cyrtia radians, sp. nov. 

 Fig. 33. Internal cast of a large specimen ; showing the general contour of the pedicle-valve, the impres- 

 sion of its dental plates and low median septum. 

 Niagara group. Milwaukee, Wisconsin. 



Cyrtia simplex, Pliillip.s. 

 Figs. 34, 35. Caidinal and protile views of an entire individual of average size ; showing the recumbent 



cardinal area and the unplicated surface. 

 Fig. 36. An enlargement of the surface of the same specimen ; showing the fine radial lines, which are 

 interrupted concentrically and produced into short .spinules. X 10. 

 Middle Devonian, Bredelar, Westphalia. 



Cyrtia alta, Hall. 



See Plate 26. 

 Fig. 37. The cardinal area of the pedicle-valve ; showing the vertical striation by the shell canals, and 



retaining the deltidial covering. 

 Fig. 38. Protile of a pedicle-valve in its normal position ; showing the inclination of the cardinal area. In- 

 cipient pli<;ations are also seen alioul the antei-ior margins of the valve. 

 Chemung group. Meadville, Peimsylvania. 



Genus SPIRIFER, Sowerby. 



Page I. 



Spirifer acuminatus, Coiuutl. 



Figs. 39, 40. Protile and cardinal views of a normal example; showing the sharply elevated median fold and 

 the duplicate jilications. 



Cornifei-ous limestone. Sandusky, Ohio. 

 Fig. 41. Internal cast of a large pedicle-valve ; showing the size and composition of the muscular area. 



Hamilton shales. Eastern Neio York. 

 Fig. 42. Intei'nal cast of the central canliniil portion of the bi-achial valve ; showing the impression of the 

 deeply striated cavity repre.senting the cardinal process, the position of the cardinal area, 

 dental sockets and socket-walls. X 4. 



Corniferous limestone. Hanover, Indiana. 



