REPORT OF THE STATE PALEONTOLOGIST I903 32 1 



<io not separate for some time and perhaps not till the neanic stage 

 is reached. 



The neanic stage is one of continuous growth. It begins with 

 the filling of the nepionic bulb and the accomplishment of the 

 withdrawal therefrom^ and ends with the cessation of the forma- 

 tion of cameras and the secretion of the last and terminal endo- 

 siphosheath. Its substages are not clearly defined but since the 

 differentiation of the endosiphocoleon and endosiphotube takes 

 place in this stage, it is possible that one substage, perhaps the 

 metaneanic, will be found to be marked by this differentiation. 

 The advance of the endosiphocone with the attendant secretion of 

 endosiphosheaths, forward growth of the endosiphocoleon and, 

 lagging behind, of the inclosed endosiphotube, persisted during a 

 great part of the individual lives of the species here under discussion, 

 as is demonstrated by the considerable length of the conch through 

 which these structures pass with but slight change. The adolescent 

 stage and notably its last or its last two substages were hence 

 remarkably long. The endosiphocoleon is decidedly the most strik- 

 ing endosiphonal structure of this stage. 



When finally maturity was reached there were still available to 

 the animal the living chamber, a very long portion of the wide 

 and open siphuncle and the endosiphocone, which was closed by 

 the last and final endosiphosheath. The latter and the last 

 formed portion of the endosiphocoleon are characterized by 

 specially thick walls, formed during ephebic age. Further growth 

 took place only by a lengthening of the living chamber at its 

 anterior margin. 



Gerontic characters have not been observed. 



The following tabulation may serve to bring out the differences 

 of the three principal growth stages of this species in more con- 

 cise form : 



