Report of the State Geologist. 



which, in the latter, are strong, distant and simple at the beginning, are Here 

 lower and closely crowded together. Their arrangement, also, shows a much 



Figures 31, 32. Protoconch and nepionic shell of Manticoceras 



rhynchostoma. x 25. 



more general variation than has been observed in Mcmtio. Pattersoni, Thus 

 the very close crowding of these varical lines may begin directly with 

 the opening of the neanic period, or may again, be delayed until this 



Fignre J3. Mantitoeerat rhyncho- Figure 34. Mantic»C4rai rhyncho- 

 noma. Side view of protoconch, itoma. Side view of external cast, 

 nepionic shell and part of neanic showing protoconch, nepionic and pro- 

 shell, x 25. longed ananeanic growth, x 25. 



phase has progressed to some degree. Intercalary lines may or may not 

 appear in the course of the first two volutions, but whether or not there, the 

 surface during this growth is closely and evenly striated. 



From the commencement of the fourth volution, the surface lines have 

 become so broadened as to appear only as flat, low festoons more elevated at 

 the umbilical margin than elsewhere but, except here, very nearly obsolete. 



At their first appearance the varices of the neanic shell are direct, w ithout 

 medial curvature, but by the beginning of the second volution a hyponomic 

 curve is distinctly developed and in subsequent stages is much more pronounced 

 than in the corresponding volutions of Mantic. Pattersoni. Notwithstanding 

 the obscurity of the concentric lines after the opening of the fourth volution, 

 the hyponomic sinus is seen to have been prominently developed at this 

 growttl stage. 



