WAVEKLY GROUP SPECIES. 316 



breadth; spire depressed conical ; volutions four or five, flattened exactly 

 on a line with the slope of the spire from the apex to near the iniddle 

 of the last turn, where there is more or less defined angle; last turn 

 large, somewhat ventricose below the angle, and produced so as to make 

 this angle near the middle of the entire bulk of the shell; umbilical 

 region a little excavated, the excavation apparently being continued^ as 

 a small perforation up into the axis ; aperture, as inferred from sections 

 of the body volution, obliquely rhombic-oval ; suture merely linear, or 

 sometimes very narrowly channeled between the middle volutions ; spiral 

 band occupying, and slightly truncating, the angle of the body volution, 

 where it is flat or a little concave, and passing around immediately 

 above the suture on the volutions of the sphere, excepting on some of 

 the upper turns, where it seems to sink nearly or quite below the suture 

 line. Surface very neatly cancellated by distinct, regular, curved, thread- 

 like transverse and revolving lines, of about equal size and distance 

 apart, the former becoming much finer and arched backward in crossing 

 the band. 



Height of a large specimen, 1.42 inches ; breadth of revolving band on 

 body volution, 0.10 inch; angle of spire, 70° to 80°. 



I was for some time inclined to think this might be the form described 

 by Dr. White and Mr. Whitfield, from the same horizon at Burlington, 

 Iowa, under the name Pleurotomaria Mississipiensis, but on comparison with 

 a sketch of the typical specimen in the Museum of the University of 

 Michigan, sent to me by Prof. Winchell, I find it to be quite distinct. 

 The type specimens of P. Mississipiensis are natural casts, but Prof. Win- 

 chell's sketches show that they difi'er from casts of the species under con- 

 sideration in having the angle of the body volution continued on those 

 of the spire distinctly above the suture, so as to give them a turreted 

 appearance instead of being all flattened exactly on a line with the slope 

 of the spire. It also has the spire mor^ elevated than that of our shell, 

 and the upper slope of the body volution concave instead of flat. Indeed, 

 White and Whitfield's species is more nearly allied to P. tabulata of Con- 

 rad, from the Coal-Measures, than it is to that under consideration. 



Locality and position : Medina, Ohio. "Waverly group of the Carboniferous, where 

 it seems to be quite abundant. 



