GASTROPODA— BELLER0PH0NTW2E. 

 In the Trenton limestone of New York, Canada, etc. 



■ , \^£ 1 



615 



Fig. 823. a-c, Salpingostoma buelli, X 2 A> '■> cl y e, S. richmondensis^ X Yi- (After 



Ulrich, Pal. Minn. ) 



XVI. Trematonotus Hall. 

 Like Salpingostoma but with a series of elongate elliptical per- 

 forations in the center of the last whorl, instead of a single long 

 slit. Siluric-Devonic. 

 43. T. alpheus Hall. (Figs. 824, 825.) Siluric. 



Fig. 824. Trematonotus alpheus, X 2 A- (After Clarke & Ruedemann, 

 Guelph Fauna. ) 



Whorls 3 to 4, scarcely impressed by preceding ones, aperture 

 with flaring lip, turning out at right angles and finally reflected, 

 frequently long. Surface with coarse flat-topped spirals, increased 

 by intercalation, and concentric wrinkles. Perforations on narrow 

 keel. 



