236 PROCEEDINGS OF THE ACADEMY OF [1888. 



B. carhonanus Meek, 1872. U. S. Geol. Sur. Nebraska, p. 224, 

 pi. iv, fig. 16 ; et pi. xi, tig. 11. 



B. urii de Kouiiick, 1873. Recherches sur les Auimaux Fossiles, 

 p. 98, pi. iv, tig. 2. 



B. carbonarius White, 1884. Geol. and Nat. His. Sur. Indiana, 

 13 rep., p. 158, pi. xxxiii, figs. 6, 7, 8. 



Abundant at the Giant mine. The shell is of medium size ; sub- 

 globose ; dorsum broadly rounded. Umbilici closed. Aperture 

 transversely semilunate, but not expanding more rapidly than the 

 uniform increase in the size of the volutions; imier lip but slightly 

 developed ; outer lip thickened and rounded towards the umbilici, 

 but becoming very attenuated towards the middle ; its medial sinus 

 rather broad, rounded and not very deep. Medial band obscure on 

 the costate portion of the shell, but on the terminal half of the body 

 whorl more or less distinct and in some specimens bordered on each 

 side by a low, narrow, yet well defined, ridge. Surface except the 

 last half of the outer whorl ornamented with from fifteen to thirty 

 or more sharp, simple, nearly 2)arallel costa?. Terminal half of body 

 whorl smooth, except along the medial portion which is often marked 

 by lines of growth, and sometimes by the low ridges, to which 

 reference has already been made. 



The form considered here under the name of Bellerophon urii is 

 the one usually designated by American pala?ontologists as B. car- 

 bonco'lus Cox. A careful comparison of the descriptions and figures 

 of the various writers on this group of Gasteropoda, and a large 

 series of specimens fails to furnish any valid reason for separating 

 specifically the American from the European form described by 

 Fleming in 1828 as Bellerophon nrii. Norwood and Pratten referred 

 Cox's specimens to B. nrii ; but Cox in 1857 made it the type of a 

 species Avhich he called B. carbonarius, distinguishing it from the 

 European form by the slight lateral expansion of the mouth and 

 particularly by the less number of revolving costje, which in B. 

 carbonarius Avere said to vary fi'om nineteen to twenty-five, while 

 according to deKoninck B. urii had from thirty-six to thii-ty-eight. 

 Though de Koninck does make this latter statement in his earlier^ 

 work, his later Recherches' state that the number varies from twenty- 

 two to thirty. McChesney in the description of his B. blaneyamis 

 seems also to have made the chief distinctive character between his 



1 Descriptions des Animaux Fossiles, p. 356. (1844.) 

 ' Recherches sur les Animaux Fossiles, p. 9S. (1873). 



