GIRTY, THE WEWOKA FORMATION OF OKLAHOMA 141 



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

 gate quadrangle, Okla. 



Ianthinopsis gouldiana sp. nov. 



Shell rather large, subovate; length a little less than 1.5 times the greatest 

 width. Aperture about three fourths the entire height ; spire about one eighth 

 of the whole. Volutions four or five, rather inflated, especially above, so that 

 the upper surface of the volution appears flattened and not strongly oblique 

 to the horizontal. Aperture fusiform, more than twice as long as wide. 



Surface smooth but marked on the more gibbous portion with a few (four 

 or five) rather coarse but faint revolving stripe. Axis solid. 



The affinities of this type, represented as it is by only one specimen, are 

 much in doubt. If it were not for the sculpture and for the shape with 

 the most prominent part of the volutions so high up, this shell might be 

 placed under Sphcerodoma in the same series with 8. intercalaris and 

 S. primigenia. The striation, though faint, is unmistakably visible in a 

 good light, but it can only be seen in the region of the aperture. The 

 shape has doubtless been somewhat modified by compression, but not suffi- 

 ciently to have produced the present result from a shell originally having 

 the proportions of either of the species named. 



On the assumption that the peculiarities presented by this form are in- 

 herent, it may be compared with the singular species described by Meek 

 and Worthen under the name Pleurotomaria ? tumida. While clearly 

 distinct from P. ? tumida, the resemblance in a general way is so strik- 

 ing that it would appear to be ultraconservative not to conclude that it 

 is a generically related species. The most important difference of a 

 fundamental kind is found in the statement by Meek that the columella 

 of the Illinois form is perforated ( ?), while that of the Wewoka shell is 

 certainly solid. 



Meek had not observed the presence of a slit band in P. (?) tumida, 

 and justly remarked that that species differs materially in outline from 

 the usual form of Pleurotomaria. Suspecting that it was a representa- 

 tive of a new genus, he provisionally proposed the name Ianthinopsis. 

 I am ready, without having determined the absence of a slit band, to 

 accept 7. tumida as representing a new generic type, and I am employing 

 Ianthinopsis for the type specimen and for the Oklahoma shell also. 



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



