PLATE LVI. 



PAGE. 



Fig. 1. Rhytimya cehana, n. sp 689 



View of the specimen described. Middle beds of the Cincinnati group, Cincinnati, O. 



Figs. 2-3. Rhytimya con vex a, n. sp 691 



Right side and cardinal views ot a large and well preserved example. The original 

 shows remains of radial series of pustules on the post-ventral slopes, but their 

 significance w is not appreciated until it was too late to change the drawing. 

 Middle beds of the Cincinnati group, Cincinnati, Ohio. 



Figs. 4-5. Rhytimya byrnesi Miller, sp 689 



Left side and dorsal views of a large cast of the interior. In figure 5 the linear de- 

 press on on eich side of the hinge line has been reproduced too much like an 

 escutcheon. Upper beds of the Cincinnati group, Richmond, Indiana. 



Figs. 6-9. Rhytimya producta, n. sp 688 



6 and 7. Right side and dorsal views of the largest specimen seen. Middle beds of the 



Cincinnati group, Mt. Sterling, Kentucky. 

 H. Right side of another specimen preserving more of the concentric lines. 

 9. An unusually short but otherwise typical example. This and the preceding one are 



from Cincinnati, Ohio. 



Figs. 10-12. Rhytimya radiaTa, n. sp '. 692 



10 and 11. Two specimens preserved in soft shale and retaining the outline and surface 

 • markings. Lower beds of the Cincinnati group, Covington, Kentucky, and Cin- 

 cinnati, Ohio. 

 12. A small part of the ventral slope x3, to show the grano-lineate ornamentation. 



Fig. 13. Rhytimya compressa, n. sp 692 



A right valve, imperfect at the posterior end but otherwise in a good state of preserva- 

 tion. Middle beds of the Cincinnati group, Cincinnati, Ohio. 



Figs. 14-15. Rhytimya MtcKLEBOROUGHi, Whitfield 690 



Left side and cardinal views ol a specimen showing the usual characters of the 

 species. The height has been reduced by pressure to perhaps four-fifths of what 

 > it was originally. Middle beds of the Cincinnati group, Cincinnati, Ohio. 



Figs. 16-17. *Whiteavesia cincinnatiensis, Hall arid Whitfield .' 656 



16. A large and nearly perfect cast of the interior of a right valve, showing the true 



form ot the species, the anterior muscular scar, traces of the posterior scar, and 

 unusually distinct rays on the ventral slope. The latter as a rule are very ob- 

 scure, while the exterior of the shell generally exhibits faint radiating lines on 

 the cardinal slopes which in rare cases may be distinguishable even on casts of 

 the interior. 



17. Hinge of a right valve, showing its simple character. Lower beds of the Cincinnati 



group, Covington, Kentucky. 



Figs. 18-20. Whiteavesia kentonensis, n. sp 658 



18. A large left valve, imperfect anteriorly and unusually high posteriorly. The 



specimen preserves small patches of the shell. 

 19 and 20. Two views of a small cast of the interior, showing the usual characters of 

 the species. Lower beds of the Cincinnati group, Covington, Kentucky. 

 Figs. 21-22. Whiteavesia pholadiformis, Hall sp 658 



21. The greater part of the hinge of a left valve. 



22. Hinge of a right valve, imperfect at both ends. 



*In the text the genus for this and the next two species reads Aclinomva. This name having 

 been preoccupied a tew years ago by Mayer for a Cretaceous genus of shells, it cannot be used for 

 these Lower Silurian types. The name Whiteavesia is therefore proposed instead. I am not sorry 

 for the change, since it affords me an opportunity of expressing my high appreciation of the 

 paleontological labors of Prof. J. F. Whiteaves ot the Canadian Geological Survey. 



E- O Ulrich. 



