GUELPH FAUNA IN THE STATE OF NEW YORK 183 



FIG. 



6 A nearly complete individual, showing the gradual obsoles- 



cence of the costae on the living chamber. From a gutta- 

 percha impression of a natural mold 



7 An older, nearly complete individual, showing the tangential 



direction of the gerontic portion of the conch 



8 Section showing the lateral compression of the conch and the 



position of the siphuncle 



9 Part of a mature individual, showing the size and expansion 



of the living chamber, and the surface sculpture on the 



mature shell 



All figures except 3 are natural size. The originals of fig. i, 

 2, 4, 6 and 8 are from the Lower Shelby bed (N. Y. State 

 Museum) ; those of fig. 3, 5, 7 and 9 from Rochester (Arey 

 collection). 



