REPORT OF TI-IE STATE PALEONTOLOGIST I9O3 315 



lamellae formed on the outside of the endosiphocones, demon- 

 strates that the wings were formed successively on the acute 

 •edges of the flattened posterior part of each new endosiphocone 

 [see text fig. 14], thus leaving with advancing growth and the 

 formation of new embracing endosiphosheaths this series of 

 conchiolinous margins behind. As to the middle portion of the 

 endosiphocoleon we have shown that in our species this is 

 formed within the apical portion of the endosiphocone or visceral 

 cone and is hence always surrounded by the endosiphosheath. 

 The fact of the presence of the anterior portion of this endosipho- 

 coleon within the endosiphocone indicates, in our opinion, that 

 it kept growing continuously at its anterior end and during a 

 greater part of the lifetime of the animal (probably from the 

 beginning of the nepionic stage to that of the ephebic stage) ; 

 this growth within the endosiphocone being preparative of an 

 approaching withdrawal of the animal and the subsequent forma- 

 tion of a new endosiphosheath. The very gradual disappearance 

 in our specimens of the endosiphocoleon posteriorly by a replace- 

 ment of the conchiolinous material by organic lime carbonate, 

 without a notable diminution in width, is taken by us as a fur- 

 ther argument of the gradual formation at the anterior end of 

 the organ and a corresponding gradual absorption posteriorly [see 

 text fig. 1 3].- With this gradual absorption of the posterior endo- 

 siphocoleon went hand in hand the new formation of the almost 

 capillary but strong walled endosiphotube. 



While we thus hold that in the species in question the forma- 

 tion of the endosiphocoleon was not delayed till maturity, but 

 took place during the entire ephebic stage, we are quite convinced 

 that maturity with its cessation of siphuncular growth and ad- 

 vance of the animal led to a longer continued secretion of 

 •conchiolinous matter at the posterior parts of the visceral cone 

 and in the anterior part of the endosiphocoleon, thus producing 

 the thick conchiolinous deposit observed in such specimens where 

 the siphuncle has attained approximately its maximal width, 

 while in siphuncles of still small diameter these same parts, even 

 •close to the endosiphocone, are provided with much thinner walls. 



