440 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.56. 



Figs. 25-28. Platystrophia brachynota (Hall), p. 408. 



25. Cardinal view illustrating the short hinge. 



26. Brachial valve of the same specimen. The figure shows the five plications 



on the fold. 

 Niagarian group (Louisville limestone), Louisville, Kentucky. 



27. Pedicle valve. The presence of four plications in the sinus is characteristic. 



28. Brachial valve of a small specimen. 



Albion group (Brassfield limestone), Nelson t'ounty. Kentucky, 

 Figs. 29-31. Platystrophia. species. 



29. Brachial valve. The fold scarcely rises above the general convex outline. 



30. Cardinal view. 



31. Pedicle valve. The shallow sinus it- characteristic. The plication pattern of 



the fold and sinus shows that this species belongs to the biplicate group. 

 Middle Ordovician ( Wesenberg limestone), near Wesenberg, Esthonia, Russia. 

 Figs. 32-35. Platystrophia, spec ius. 



32. Cardinal view showing the shoft hinge-line and globose form. 



33. Brachial valve. The three plications of the fold is typical. The varices are 



so strong as to be almost lamellote. 



34. Pedicle valve. 



35. Anterior view. This species has two plications in the sinus. The plication 



pattern of the fold and sinus places this species in the biplicate group. 

 Upper Ordovician (Fl) Kiu-kiill, Russia. 

 Figs. 36-38. Plastystrophia rhynchonelliformis, new species, p. 413. 



36. Brachial valve showing a compressed fold. 



37. Pedicle valve. The triplicate arrangement of the plications of the sinus is 



typical. 



38. Cardinal view. The short hinge line is typical. 

 Trenton limestone Ellisburg, New York. 



Figs. 39-41. Platystrophia extensa, new species, p. 410. 



39. Pedicle valve showing the triplicate plication pattern. 



Trenton group (Hermitage limestone), two miles north of Hartsville, 

 Tennessee. 



40. Cardinal view. The thin valves are characteristic. 



41. Brachial valve. 



Trenton group (Hermitage limestone), Auburn, Tennessee. 

 Figs. 42-43. Platystrophia daytoncnsis laurelensis, new variety, p. 406. 



42. Brachial valve showing the presence of three plications on the fold. 



43. Pedicle valve. The two plications in the sinus show the biplicate arrange- 



ment. 

 Niagara group (Laurel limestone), St. Paul, Indiana. 



Plate 43. 

 All figures on this plate are natiu-al size. 

 Figs. 1-8. Platystrophia amoena, new species, p. 412. 



1. Brachial valve. The figure shows the low spreading fold . 

 Trenton group (Bigby limestone), Cynthiana, Kentucky. 



2. Brachial valve of a mutation which has six plications on the fold. 



3. Brachial valve of a normal individual. 

 Trenton limestone, Trenton Falls, New York. 



4. Brachial valve of a narrow specimen. 



5. Anterior view showing the low fold, shallow sinus and thin valves. 



6. Pedicle valve of a normal indi\ddual. 



Trenton group (Bigby limestone), Versailles, Kentucky. 



7. Pedicle valve of a mutation which has four plicationa in the sinus. 

 • 8. Brachial valve of a normal individual. 



Trenton group (Bigby limestone), Frankfort, Kentucky. 



