CEPHALOPODA— ORTHOCHOANITES. 87 



loi. S. hartti (Dawson). Carbonic. 



Loose coiled gyroceracones ; whorls subquadrate, with two broad 



flutings at the sides, and two narrower flutings at the ventral 



Fig. 1305. Stroboceras trisulcatum. (After Meek and Worthen, 111. Pal., II.) 



margins; venter flat, dorsal surface regularly rounded; siphuncle 

 near ventral margin. 



Windsor limestone of Nova Scotia. 



XXXII. Apheleceras Hyatt. 



Gyroceracones and nautiUcones of moderate involution; adult 

 with hollow or channeled venter, compressed whorls and without 

 the revolving ridges characterizing the preceding genus; sutures 

 with ventral and lateral lobes, and broad, dorsal saddle. Mis- 

 sissippic. 



102. A. disciforme (Meek and Worthen). (Fig. 1306.) 



Mississippic. 



Large, disc-like, with sides of whorls gently convex, and more 

 strongly arched towards the venter which is doubly channeled. 



Keokuk of Illinois. 



XXXIIL Ephippioceras Hyatt. 



Nautilicones differing from the preceding genera in having sub- 

 acute, prominent, ventral saddles near the shoulders, and broad, 



