GIRTY, THE WEWOKA FORMATION OF OKLAHOMA 153 



these four lobes and saddles in the matter of width. If anything, the ventral 

 saddle and the small lateral saddle are a little wider than the two lobes. The 

 large lateral saddle and lobe are about equal, moderately narrow, with some- 

 what sigmoidal sides. The suture seems to form part of another large, 

 rounded asymmetrical saddle. Only part of the outer limb of this is retained 

 on the only specimen found, but probably the remainder appeared on the con- 

 fines of the visible suture not exposed in the type. 



This species is most closely related to D. lenticulare, from which it has 

 been discriminated because of the suture. The differences manifested in 

 this feature can hardly be ascribed to difference in age, because the two 

 type specimens must have been nearly of a size and presumably at a corre- 

 sponding stage of development. The differences noted are the narrower 

 ventral saddle, the pointed instead of rounded shape of the first small 

 lobe, and the much elongated shape of the second. The outer sides of the 

 first large lobe are also more approximate. D. Oklahoma differs from 

 D. texanum in about the same characters as those pointed out for D. len- 

 ticulare, but is rather more closely related. This is shown, for instance, 

 in the first small lobe, which is pointed in Oklahoma and texanum, but 

 rounded in lenticulare. 



Horizon and locality : Wewoka formation ; Wewoka quadrangle, Okla. 



Gonioloboceras welleri var. gracile var. nov. 



This species attains a diameter of 53 mm. in a fragment entirely septate. 

 The type specimen, however, has a diameter of 43 mm., with a thickness 

 through the center of 14 mm. The umbilici are small, only 3 mm. wide, and 

 the whorls highly involute. The sides are gently convex, contracting to a 

 very narrow venter marked by a revolving channel guarded by two thin, 

 angular ridges. In the early stages the shell is less compressed and the venter 

 less distinctly channeled. When still younger, the venter was probably rounded, 

 but the two carinne with their inclosed groove are largely a development of 

 the test and do not show clearly on the internal mold. The surface appears 

 to be marked by obscure, incremental lira?, the direction of which indicates 

 a deep, bi'oad, hyponomic sinus. 



The suture consists of two lobes and two saddles on each side, together with 

 a high, broad, siphonal saddle. This is rounded, but with a notch (?) on the 

 median line. The latter feature is not clear. The suture lines bend sharply 

 backward near the middle, but in most specimens they appear to be discon- 

 nected. In one, however, they appear to connect into a small V-shaped re- 

 entrant angle. The second saddle is broad and unsymmetrical. The first 

 saddle and the two adjacent lobes are very nearly equal, the second lobe being 

 slightly broader. They are subangular, but not acutely pointed. The sutures 

 are closely arranged, the inner sides of the first saddles being almost in 

 contact. 



