214 GASTBROPODS. 



Shell large, heavy, subglobose, spire depressed ; volutions 

 six in number, rapidly increasing in size from the apex, last one 

 very large and ventricose. Aperture ovate; outer lip abruptly 

 becoming sharp. Oolumella smooth. Surface glabrate, with 

 faint lines of growth. 



Horizon and localities. Upper Carboniferous, Coal 

 Measures: Kansas City. 



The form described by Shumard as Macrochilus texanus 

 appears to be merely the immature shell of Swallow's 8. pon- 

 derosa. In individuals of the former the fold on the columnella 

 is quite pronounced, while in the latter species it is scarcely 

 noticeable. By making away the body whorl, however, in 8. 

 ponder osa, the revolving fold is found to rapidly increase in size 

 and prominence ; while a comparison of a large series of this 

 species, of all sizes, shows that the fold on the collumella is 

 really much more pronounced in the younger individuals, which 

 cannot be told from the ordinary 8. texana. 



Sphaerodoma littonana (HALL). 



Natica Uttonana Hall, 1858: Trans. Albany Inst., vol. IV, p. 30. 

 Naticopsis littonana Meek & Worthen, 1866: Proc. Acad. Nat. Sci.. Phila., 



p. 268. 

 Naticopsis littonana, var. genevievensis Meek & Worthen, 1866: Proc. Acad. 



Nat.Sci., Phila., p. 268. 

 Macrochilus littonanum Whitfield, 1882 : Bui. Am. Mus. Nat. Hist., vol. 



I, p. 73, pi. viii, fig. 28. 

 Macrochilus littonanum Hall, 1883: Geol. Sur. Indiana, 12th Ann. Kept., 



p. 369, pl.xxxi, fig. 28. 



Sphcerodoma littonana Keyes, 1889: Proc. Acad. Nat. Sci., Phila., p. 305. 

 Macrochilina littonana Miller, 1890 : N. A. Geol. and Pa.'., p. 409. 



Shell very small, globose; spire of small size, somewhat 

 elevated ; volutions four, last one extremely large and ventri- 

 cose. Aperture ovate. Surface showing only lines of growth. 



Horizon and localities. Lower Carboniferous, Kaskaskia 

 limestone : Ste. Genevieve. 



