GASTROPODA— EUOMPHALIDJE. 659 



Black River of Paquettes Rapids, Canada ; Trenton of Mis- 

 souri ; Stones River of Illinois (var. robustd). A somewhat lower- 

 spired form, with wider and shallower umbilicus, deeper notch, and 

 fainter spirals (H. umbilicata U. and S.) occurs in the Stones River 

 of Minnesota, Wisconsin, and Illinois. 



177. H. tennesseensis Safford. (Fig. go6,j,£.) Ordovicic. 

 Like the preceding, but without the spirals ; suture slightly 



•canaliculate. 



Very abundant in lower Stones River of Tennessee, also in Black 

 River; Stones River and Black River of Kentucky. [H. planul- 

 atoides Ulrich.) 



LVI. Pleuronotus Hall. 



Shells with flat or concave spire and broad, shallow umbilicus ; 

 apertural notch deep ; a distinct 

 revolving band present. Siluric(?) 

 — Devonic. 



178. P. decewi Billings. (Fig. 



907.) Devonic. 



Large, spire flat or gently con- 

 cave, of three or four volutions, 

 periphery in adult flat and sepa- 

 rated from the upper surface by 



a Strong carina. ¥\G. go"j . Pleuronotus decewi. (After 



Onondaga of New York, Can- Hall.) 

 ada, Ohio, Michigan, and elsewhere. 



LVII. Euomphalus Sowerby. 



Shells with flat or low spires, angulate and carinate above, but 

 without marked notch as in Pleuronotus. Young like Straparollus. 

 Carbonic. 



179. E. latus Hall. (Fig. 908.) Mississippic. 

 Of about four or five volutions, spire very little elevated, upper 



surface obliquely flattened inside of carina, outer margin angulate 

 and subcarinate ; inner abruptly elevated and somewhat carinate 

 at suture line ; base broadly umbilicate. 



Burlington of Iowa, Illinois, Missouri ; Waverly of Ohio. 

 J 80. E. similis M. and W. (Fig. 909.) Mississippic. 



Small, subdiscoidal, spire flat in var. planus, otherwise slightly 



