Weller — Kinderhook Faunal Studies. 461 



but that species does not have the outer volution free and is 

 apparently a true Sirojphostylus. 



Orthonychia jeffersonensis n. sp. 



Plate 2, figs. 38-39. 



Description. Shell subpyramidal in form, slightly oblique , 

 higher than wide, subsemicircular in cross-section, the sides of 

 the shell slightly convex from the apex to the margin of the 

 aperture except at the side towards which the obliquity of the 

 shell is directed which is nearly straight or slightly concave. 

 The surface marked by vertical plications and by rather fine, 

 more or less irregular lines of growth which follow the sinu- 

 osities of the aperture. 



The dimensions of a typical specimen are: height 22 mm., 

 diameter of aperture 16.5 mm. 



Remarks. This species does not closely resemble any of 

 the Hamilton species of the genus nor any of those present in 

 the Kinderhook or other Mississippian faunas. 



Orthonychia unqula n. sp. 



Plate 2, figs. 36-37. 



Description. Shell arcuate and slightly [twisted, com- 

 pressed, entirely uncoiled, expanding gradually from apex to 

 aperture, the aperture subelliptical in outline. Surface 

 marked by more or less coarse and irregular lines of growth , 

 giving to the shell, sometimes, a very rough appearance. 



The dimensions of the type specimen are: height 26 mm., 

 maximum diameter of aperture 10 mm., minimum diameter 

 of aperture 6.5 mm. 



Remarks. This species is entirely unlike any of those 

 recognized in either the Mississippian or the higher Devonian 

 faunas. It may be easily recognized by its peculiar claw- 

 shaped form. One of the specimens referred to the species 

 is more curved, more rapidly expanding and smoother than 

 the type specimen, and it should possibly be considered as a 

 distinct species. 



