152 ANNALS NEW YORK ACADEMY OF SCIENCES 



umbilical zone. The internal sutures consist of three tongue-shaped lobes of 

 very nearly equal size and shape, two rounded saddles, also nearly equal, and 

 half of two others, one at either margin, each being interrupted by the limit of 

 the depressed zone. 



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

 gate quadrangle, Okla. 



Dimorphoceras lenticulare sp. nov. 



This species is known only from one or two fragments but tbe characters 

 shown are sufficient for a fairly complete description. 



The shape is discoidal, much thicker at the umbilicus than at tbe venter. 

 The size indicated is about 40 mm. in diameter and about 13 mm. in thickness. 

 As only the septate portion is known, complete specimens must have been con- 

 siderably larger. The umbilicus was small and the shell highly involute. The 

 shape of tbe whorl section is somewhat triangular, slightly higher than 

 broad. The sides are gently convex, strongly and regularly contracting to the 

 ventral surface, which is narrow and sharply rounded. Probably, there was a 

 more or less distinct umbilical shoulder and a narrow umbilical zone. 



There is a broad, rounded ventral saddle with a median notch. The lateral 

 sutures consist of two parts, that toward the umbilicus having large turns and 

 that toward the venter having small ones. The small folds, which comprise 

 two lobes and a saddle, can be thought of as a large lobe coordinate with those 

 toward the umbilicus, which has been divided by a median saddle. The three 

 plications thus formed are nearly equal, but the first lobe and the saddle are 

 rounded, while the second lobe is tongue-shaped. The saddle is a little nar- 

 rower than the two lobes, and the second lobe projects a little farther back- 

 ward than the first. The remainder of the suture consists of high angular 

 plications, a saddle and a lobe, together with the major part of another saddle, 

 all of which probably comes within the limits of the visible suture when fully 

 exposed. These lobes and saddles are asymmetrical and have more or less 

 sigmoidal sides. They are so arranged that the point of the lateral lobe is 

 almost in contact with the outer side of the preceding lobe somewhat less than 

 half-way up. The final saddle is broad, rounded and asymmetrical. 



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

 gate quadrangle. Okla. 



Dimorphoceras oklahomae sp. nov. 



Shell lenticular in shape, thick in the middle, thin at the edges. Diameter 

 50 mm., thickness 20 mm. Highly involute with small umbilici (about 

 5 mm.). The whorl section is more or less triangular, with gently convex, con- 

 verging sides, and narrow, strongly rounded venter. Umbilical shoulder dis- 

 tinct ; umbilical zone narrow. 



Ventral saddle rather narrow, indented on top. The two small ventral lobes 

 are pointed and tongue shaped, the first one short, the second long and narrow. 

 The saddle between them is rounded. There is not much difference between 



