ART. 17 MOLLUSKS FROM WYOMING EEESIDB AND WEYMOUTH H 



than 90° ; anterior margin broadly convex, basal margin very gently 

 convex, posterior margin narrowly convex; posterior umbonal ridge 

 poorly defined. Surface shows only fine concentric lines of miequal 

 elevation. Internal characters entirely unknown. 



Length, 18 millimeters; height, 16 millimeters; depth of valve^ 

 4 millimeters. 



The original Mactra ? incompta came from a locality 5 miles above 

 Pueblo, Colo., probably in the Carlile shale, though possibly older. 



PJe^iotypes.—C?it. No. 73771, U.S.N.M. 



MACTRA? ASPENANA, new species 



Plate 1, Figure 11 



A single mold of the exterior of a valve represents a species simi- 

 lar in general expression to Mactral incompta White? but differing 

 enough in outline to deserve record as a different species. It is much 

 longer proportionately and shallower though also a small species 

 with a sculpture of fine unequal concentric lines. None of the species 

 of similar age is near it, though it suggests the much younger 

 Mactra? canonensis Meek.^° Internal characters entirely unknown. 



Length, 20 millimeters; height, 14 millimeters; depth of valve, 

 3 millimeters. 



Eolotype.—Cfit. No. 73772, U.S.N.M. 



Family ACANTHOCERATIDAE Douville 

 KANABICERAS, new genus 



Stanton-^ in 1894 described from a lower Turonian horizon near 

 the base of the local Cretaceous section at Upper Kanab, Utah, the 

 ammonite Acanthocevasf kanahense. It was not figured again until 

 1927, when Moreman — published a figure of a specimen from the 

 Turonian part of the Eagle Ford shale of north Texas that shows 

 features not present in the type of tlie species. Adkins ^^ has sug- 

 gested that Moreman's species is not Stanton's species and that the 

 latter may belong to Protacanthoceras Spath.-* A comparison of the 



» White, C. A., Contributions to invertebrate paleontology, No. 1 : Cretaceous fossils of 

 the Western States and Territories : U. S. Geol. Geog. Survey Terr., Eleventh Ann. Rept. 

 (1877), p. 297, pi. 9, flff. 11, 1879. 



=1 Stanton, T. W., The Colorado formation and its invertebrate fauna : TJ. S. Geol. Sur- 

 vey Bull. 106, p. 181, pi. 36, figs. 6-8, 1894. 



■^Moreman, W. L., Fossil zones of the Eagle Ford of north Texas: Journ. Paleontology, 

 vol. 1, p. 95, pi. 13, fig. 5, 1927. 



=3 Adkins, W. S., Handbook of Texas Cretaceous fossils: Texas Univ. Bull. 2838, p. 245, 

 1928. 



^ Spath, L. F-, On the ammonite horizons of the Gault and contiguous deposits : Geol. 

 Survey Great Britain Mem., Summary Progress for 1922, p. 144, 1923. 



Sharpe, Daniel, Description of the fossil remains of Mollusca found in the chalk of 

 England, Part I, Cephalopoda : Palcontographical Soc. Mon., p. 25, pi. 9, fig. 3, 1853. 



