Fig. 25. 
Fig. 26. 
Fig. 27. 
Fitj-. 28. 
PLATE XXXIX—Continued. 
Genus CYliTlNA, Davidson. 
Page 43. 
See Plates 25, 28. 
CVKTINA, sp. ? 
An enlargement of the surface ; showing the bases of concentric rows of spinules. X 4. 
Caidinal view of an infernal cast of the pedicle-valve, broken so as to show the convergent dental 
plates uniting with the median septum, and the slight projection of the edge of thelattei- within 
the spondylium thus formed. 
The same specimen viewed from above; showing the length of the median septum. 
An enlargement of a poi-tion of the intei’ior of the pedicle-valve ; showing the convergence of the 
dental plates, and the projection of the median septum beyond their union. X 3. 
Chert-beds of the Burlington limestone. Burlington, loiua. 
Genus SYKINGOTHYRIS, Wincheul. 
Page 47. 
See Plates 25, 26, 27. 
Syringothykis Missouri, sp. iiov. 
Figs. 29-31. Thi'ee views of the typical specimen ; showing its small size, elevated pedicle-valve, broadly 
rounded cardinal margins, and coarse lateral plications. Internally this shell has the syringo- 
thyroid tubifei-ous plate, and the shell-substance is highly punctate. 
Choteau limestone. Bike county, Mis.'souri. 
Genus CYRTIA, Dalman. 
Page 40. 
See Plates 21, 25, 26, 28. 
Cyrtia ExroitREOTA, Wiihleiihcrg’, vtir. arrecta, Hall and Whittield. 
See Plate 28. 
32. View of the umbonal cavity of the conjoined valves; showing the foramen, the strong dental 
plates, and the articulating apparatus. X 2. 
Niagara group. Louisville, Kentucky. 
Fit 
Cyrtia radians, sjt. iiov. 
Fig. 33. Internal cast of a lai-ge specimen ; showing the genei-al contour of the pedicle-valve, the impres¬ 
sion of its dental plates and low median septum. 
Niagara-grouj). Mihoaukee, Wisconsin. 
Cyrtia simplex, Phillips. 
Figs. 34, 35. Cardinal and profile views of an entire individual of average size ; showing the recumbent 
cardinal area and the implicated surface. 
Fig. 36. An enlargement of the surface of the same specimen; showing the tine radial lines, which are 
interrupted concentrically and produced into short spinules. X 10. 
Middle Devonian, Bredelar, Westphalia. 
Cyrtia alta, Hull, 
See Plate 26. 
Fig. 37. The cardinal area of the pedicle-valve ; showing- the vei'tical striation by the shell canals, and 
retaining- the deltidial covering. 
Fig. 38. Profile of a pedicle-valve in its normal position ; showing the inclination of the cardinal area. In¬ 
cipient plications are also seen about the anterior margins of the valve. 
Chemung group. Meadville, Penmylvania. 
Genus SPIRIFER, Sowerby. 
Page 1. 
SpIRIFER acuminates, CoiU'ild. 
Figs. 39, 40. Pi-ofile and cardinal views of a normal example; showing the shai-ply elevated median fold and 
the duplicate plications. 
Corniferous limestone. Sandusky, Ohio. 
Fig. 41. Internal cast of a large pedicle-valve ; showing the size and composition of the muscular area. 
Hamilton shales. Ea.stern Neio York. 
Fig. 42. Internal cast of the central cardinal portion of the bi-achial valve ; showing the impression of the 
deeply striated cavity representing the cardinal pi'ocess, the position of the cardinal area, 
dental sockets and socket-walls. X 4. 
Corniferous limestone. Hanover, Indiana. 
