54 



Report of the State Geologist. 



these are once developed they occur at subequal intervals and are of equal 

 size, sometimes for an entire volution, sometimes for a less distance. The dura- 

 tion of such subequal lamellae seems to be a wholly individual character. 



Figure 23. Vertical section of 

 nepionic and neanic whorls, x 10. 



Figure 24. Side view of entire neanic 

 shell, showing protoconch, the swollen ana- 

 nepionic, contracted paranepionic and ex- 

 panded metanepionic stages, the abrupt 

 termination of the nepionic stage, the 

 regular, distant and equal varices of the 

 ananeanic stage, followed by tie introduc- 

 tion of a subordinate series, x 10 



Yet in all there is a well denned ananeanic substage in which the ornament 

 consists solely of these lamellae. Upon looking into the umbilicus of a well 

 preserved adult in which portions of all whorls and protoconch are exposed, 

 it will be observed that for one and a half or even two volutions beyond the 

 nepionic shell only such simple and equidistant lamelhe are exposed. This, 

 however, does not mean that only such are. present on these younger whorls, 

 for actually, after about a semivolution of ananeanic growth there appear 

 intercalary lamellae, at first one between each two of the ananeanic or primary 

 series. In this mode the intercalation may proceed with marked regularity 

 for a considerable period, the intercalary lamelhe, at first short and wholly 

 restricted to the venter and ventrolateral surfaces, become longer and, 

 with the primary lamelhe, extend to - the dorsal furrows. After the 

 intercalation has become established it may be continued by the appear- 

 ance of two secondary lamelhe, and these of equal size. With growth, the 

 secondary interspaces also receive a third set of lamelhe. At the commence- 

 ment of the third whorl the lamellae have become of subequal size, relatively 

 crowded, and likew ise relatively smaller in comparison w ith the size of the 

 whorl. In immediately ensuing stages the ornament progressively approxi- 

 mates the character of a simple striatum and the full reduction of the 

 lainella; to this condition is among the characters of epheby. 



