GIRTY, THE WEWOKA FORMATION OF OKLAHOMA 137 



Orestes nodosus sp. nov. 



Shell small, irregularly conical. Diameter of last whorl about equal to the 

 greatest height, sometimes less. Height of last volution about equal to the 

 height of the spire above. Volutions angular, most prominent below the 

 middle. Spire somewhat turreted. Umbilicus apparently closed, but with 

 the lower lip folded backward upon itself so as to produce a small pit or false 

 umbilicus. Suture considerably depressed. The sbell projects strongly from 

 the suture, then bends downward and is flat or concave below to the first 

 carina. Thus the upper third of the upper surface forms a sort of spiral 

 ridge just below the suture. The lateral surface is about one third as broad 

 as the upper surface. It consists of two rather thick, rounded carina? guard- 

 ing between them a relatively broad concave channel in which the band is 

 situated. The upper carina is better defined than the other, but does not 

 project quite as far. The lower surface is nearly horizontal, gently convex, 

 more tumid near the umbilicus. The swollen band below the suture is marked 

 by a row of distantly arranged nodes which appear to be independent of the 

 superficial sculpture. 



The surface is crossed by regular and nearly equal revolving and transverse 

 lira? of which the former are heavier and dominant, while the latter are 

 more closely arranged. The upper surface carries about five (four to six) 

 revolving lines, arranged at regular and distant intervals. The upper one is 

 situated on the subsutural prominence. An additional lira is occasionally 

 developed just above the latter, which gives the nodes a somewhat elongated 

 double- topped appearance. The upper of the two carina? bounding the slit is 

 a similar revolving lira of somewhat larger size and so is the lower one. Just 

 within these two lira? are two small edges which define the true limits of the 

 slit band. The band is medially traversed by another fine, revolving thread, 

 or rarely by three. The lower carina carries about two fairly heavy lira?, 

 while the lower surface is crossed by about twelve others, some of which may 

 be fine, and alternating with those of larger size. They are heavier and more 

 crowded than the lira? above. The transverse lira?, doubtless following the 

 outline of the aperture, bend strongly backward, being convex near the suture 

 and straightened or gently concave near the band. Over the latter, they are 

 deeply concave, producing fine, regular, closely arranged erenulations or 

 lunules. On the under side, they run obliquely backward with a strong convex 

 turn on the lower carina. For most of the distance, they are thus nearly 

 straight. In the region of the suture, they seem to be fine, irregular and 

 crowded, passing just below the nodose zone into regular, rather distant lira? 

 which give a finely nodose appearance to the upper carina and generally tend 

 to produce little prominences where they cross the revolving lira?. Even 

 below the nodose zone, fine, intermediate, incremental lines are more or less 

 conspicuous. The transverse lira? do not produce erenulations on the project- 

 ing edges of the band, but they have this effect to a greater or less extent on 

 the revolving line or lines which traverse it. 



The volutions embrace up to the edge of the band of the preceding one. 

 They are about five in number. 



Horizon and locality: Wewoka formation; Wewoka quadrangle, Coal- 

 gate quadrangle, Okln. 



