50 



can Philosophical Society, Vol. XXXII, p. 525. The genus was 

 founded on a fragment of a cast from an unknown locality and 

 named B. impressum. If we are correct in referring our species to 

 his genus, it will serve to fix the geological range of his species and 

 possibly point toward the locality. Our specimen is from what is 

 called by the local collectors, in Indiana, the Knobstone Group, 

 which is not very definite, but means the Keokuk Group and the 

 Waverly, where the two are not separable, and the fossils are gener- 

 ally casts. 



Our species is larger than the type. Volutions numerous. Um- 

 bilicus wide and showing almost completely each inner turn, and 

 probably perforated. The rapid enlargement of the part preserved 

 indicates a complete perforation. Transverse section subelliptical. 

 The ends in fig. 2 are altogether too round, a better idea of the 

 subelliptical section will be formed by comparing figs. 1 and 2 or 

 figs. 2 and 3. It is the way the ends are fractured that gives this 

 erroneous outline in fig. 2, drawn under a camera lucida. The 

 ventral side is depressed convex, with a subangular ventro-lateral 

 ridge on each side. Lateral sides narrowly rounded toward the 

 umbilicus. Dorsal side has a slightly concave depression or contact 

 furrow, a little less than one-third the lateral diameter of the shell. 

 The sutures have broad ventral and lateral lobes with saddles ven- 

 tro-laterally and at the commencement of the umbilicus, or they 

 might be said to be indicated by a waving line. Each one forms, 

 however, a V-shaped angle in the dorsal sinus or contact furrow. 

 The septa are distant on the ventral side, about one-half the dorso- 

 ventral diameter. At the small end of our specimen they are 

 distant a little less than half the dorso-ventral diameter and at the 

 larger end a little more than half the dorso-ventral diameter. The 

 outer shell is unknown. 



Found by G. K. Greene, in the Knobstone Group, at Sampson 

 Springs, in Clarke county, Indiana, and now in the collection of 

 Wm. F. E. Gurley. 



