76 



Report of the State Geologist. 



In the form and size of protoconch, degree of umbilication and character 

 of septation we shall find no distinction from Mcmtic. Pattersoni and its para- 

 phase Mantic. rhynchostorna ; but in respect to whorl section and ornament 

 the differences are pronounced. 59 



Figures 56-59. Manticoceras sororiurn. Fig. 56. Side view of young shell, showing suture ; Figs. 57-59. Outlines 

 showing the rapid change in whorl section. x3. 



Only in early volutions does the whorl section approach that of Mantic. 

 rliynchostorna. The rapidity with which the shell narrow s during the third 

 and fourth volutions, and passes beyond the ultimate section of adult Mantic. 

 Pattersoni, is well shown in the accompanying outlines. In the final observed 

 whorls the shell approaches, without attaining, carination. 



The ornamental lines consist at first of strong and simple varices ; these 

 maintain their simplicity for a considerable period and are remarkably strong 

 during the course of the third volution and early part of the fourth volution, 

 where in allied forms the stria' have become subdued. They are especially 

 noteworthy for their sharp curvature, the hyponomic curve being a narrow 

 and deep festoon, accompanied by strong forward curves on the hyponomic 

 ridges and broad backward curves on the lateral slopes. Although these 

 varical lines are obsolescent on the fourth whorl, they at no time assume the 

 character of pi he. 



The lateral compression of the final volution together with the character 

 of the ventral curvature of the varices, brings into prominence the venter as 

 a narrow peripheral band. 



Manticoceras sororiurn has been found only in the vicinity of Angola, on 

 the lake Erie shore and along Big Sister and Farnham creeks, Erie county. 



