GASTEROPODS. 161 



There appears to be but little doubt that the form des- 

 cribed by Conrad from the region east of the Appalachians as 

 Inachus catilloides, and Euomphalus rugosus of Hall, are identi- 

 cal. Although Conrad's original description is brief, his figure 

 shows clearly the kind of a shell he had under consideration. 

 A careful comparison of a large series of Pennsylvania speci- 

 mens and those forms from the Mississippi basin, fails to bring 

 out any differences sufficiently marked to warrant a specific 

 separation of the shells of the two districts. The form is gen- 

 erally known throughout the continental interior under Hall's 

 name. That designation, however, was preoccupied by Sow- 

 erby in 1812, and for this reason Meek and Worthen proposed 

 subrugosus for the specific title. After all, it is very probable 

 that the form should more properly be regarded as identical 

 with a certain European species ; and further comparison may 

 require the mergence of the two species now regarded as 

 valid. S. catilloideSj as now understood, is widely distributed 

 geographically, and is one of the most abundant and character- 

 istic shells of the Coal Measures of the Mississippi basin. It 

 often attains a very considerable size, though, as a rule, its 

 maximum measurement is not greater than ten or twelve milli- 

 meters. 



Straparollus pernodosus MEEK & WORTHEN. 



Straparollus pernodosus Meek & Worthen, 1870 : Proc. Acad. Nat. Sci. , 



Phila., p. 45. 

 Straparollus pernodosus Meek & Worthen.1873: Geol. Sur. Illinois, vol. V, 



p. 604, pi. xxix, figs. 14a-c. 



Euomphalus pernodosus Keyes, 1888: Proc. Acad. Nat. Sci., Phil*., p. 241. 

 Straparollus pernodosus Keyes, 1891 : Proc. Acad. Nat. Sci., Phila., p. 286. 



Shell rather large, planorbiforin, with the spire on a level 

 with the upper edge of the body-whorl ; volutions five or six 

 in number, flattened above, rounded below, with a well-defined 

 row of large nodes disappearing toward the aperture ; the upper 

 peripheral margin has a prominent carina, from which the sur- 

 face slopes inward to the suture ; umbilicus broad, moderately 

 deep, showing all the inner whorls. Surface marked by con- 



G 12 



