GUELPH FAUNA IN THE STATE OF NEW YORK 1 53 



FIG. 



5 A natural cast of the exterior of an older individual, showing 



a more nodose character of the revolving ribs upon the 

 outer lip and the cast of one of the innermost volutions 



6 The exterior of the last volution of a gerontic specimen, show- 



ing a partial suppression on the outer lip of the smaller ribs 

 which are made much too strong in the drawing. From a 

 gutta-percha impression of a natural mold 



7 Ventral view of the internal cast of the last volution, showing 



the ventral depressed zone 



8 Section of an internal cast, showing the relative width and 



hight of the volutions 



9 Another section of an internal cast, exhibiting a somewhat 



asymmetric arrangement of the inner volutions 

 All specimens drawn natural size. With the exception of the 

 original of fig. i which is from the Guelph at Rochester (Arey 

 collection), all are from the Lower Shelby bed (N. Y. State 

 Museum). 



