184 GASTEROPODS. 



in hand. In regard to Meek & Worthen's Metoptoma umbella, 

 there appear to be no good grounds for considering it as dis- 

 tinct from Hall's form. 



Igoceras pabulocrinus (OWEN). 



Plate lii, figs. 3a-b, and pi. liv, figs. 3a-l. 



Platyceras subrectum Hall, 1859 : Geology Iowa, vol . I , Supp . , p. 89. ( Not 



P. subrectum Hall, 1859.) 

 Platyceras subrectum Hall, 1860: Twelfth Ann. Reg. Kept., Univ. N. Y., 



p. 18. ( Not P. subrectum Hall, 1859, New York shell.) 

 PUeopsis pabulocrinus Owen, 1862: Geol. Sur. Indiana, p. 365, fig. 8. 

 Platyceras infundibulum Meek & Worthen, 1866: Proc. Acad. Nat. Sci., 



Phila., p. 266. 

 Platyceras extinctor Meek & Worthen, 1866 : Proc. Acad. Nat. Sci., Phila. , 



p. 266. ( Never formally proposed.) 

 Platyceras infundibulum Meek & Worthen, 1873: Geol. Sur. Illinois, vol. V, 



p. 517, pi. xvii, fig. 3. 

 Platyceras infundibulum Keyes, 1888: Proc. Am. Philosophical Soc., vol. 



XXV, p. 238, fig. 1. 



Platyceras infundibulum Keyes, 1889 : Proc. Acad. Nat. Sci., Phila., p. 289. 

 Capulus infundibulum Keyes, 1890: Am. Geologist, vol. VI, p. 9. 

 Capulus infundibulum Keyes, 1890 : Proc. Acad. Nat. Sci., Phila. , p. 174, 



pi. ii, fig. 10. 



Shell more or less conical, often somewhat oblique, with 

 usually many undefined longitudinal folds ; apical portions 

 slender, expanding regularly at first and then more rapidly. 

 Apex attenuated, often slightly deflected toward the posterior 

 side. Surface smooth, ^but toward the aperture marked by 

 numerous undulating, frequently imbricating lines of growth. 



Horizon and localities. Keokuk limestone and shales: 

 Keokuk, Iowa ; Warsaw, Illinois ; Orawfordsville, Indiana. 

 Burlington limestone : Burlington (Iowa); Springfield (Greene 

 county). 



The name pabulocrinus was given to the species under 

 consideration for the reason that the mollusk was thought to 

 form the food of crinoids, since it was often found adhering to 

 the calyx of the echinoderm directly over the opening in test. 

 This explanation appears quite plausible ; but long ago this 

 view was proved false. Owen gave practically no descrip- 

 tion of the shell ; and his figure was roughly executed, 

 showing hardly anything more than the bare outlines of the 



