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NEW YORK STATE MUSEUM 



toward the apical end. This can be easily explained by the fact 

 that the endosiphocone in its anterior part needed the most guy 

 ropes on account of the greater weight of the visceral cone there. 

 Therefore also the number of endosiphofunicles diminishes so 

 greatly from the outer zone to the next, because the outer endo- 

 siphosheath inclosed a much larger section of the visceral cone 

 at the plane of the section than the later inner endosiphosheath 

 did at the same point. 



In section I the endosiphofunicles of the outer whorl appear 

 distinctly as fine tubes with thin conchiolinous walls, their lumen 



being filled by a milk-white calcite which 

 strongly contrasts w^th the more limpid; 

 calcite crystals surrounding the tubes. 

 Many of these tubes bifurcate near the 

 ectosiphuncular wall, one several times. 

 There is secured by this mechanical con- 

 trivance a larger base of fixation, which 

 insures steadiness and freedom from 

 vibrations for the visceral cone during 

 the movements of the animal. 



Whether the numerous endosiphofun- 

 icles were but a modification of the endo- 

 siphoblades which, as we have seen, hold 

 the endosiphocoleon and endosiphosheaths 

 in position in Proterocameroceras 

 b r a i n e r d i and originated by a dissolution of these suspensory 

 membranes in numerous strands, or are a new formation induced 

 by the necessity of supporting the heavy visceral cone hanging free 

 within the broad siphuncle, is a question which we can not con- 



NOTE. We can not yet determine whether these endosiphofunicles are 

 homologous to the remarkable verticils of sometimes branching tubuU 

 which in some species of Actinoceras connect the endosiphuncle with the 

 ectosiphuncle. Both undoubtedly are quite similar in appearance. The 

 tubuli of Actinoceras [^^^e. g. Actinoceras abnorme Hall, N. Y.. 

 State Mus. 20th An. Rep't, pi. t8, fig. 10 (copied here after Zittel)] are by 

 Foord described in Actinoceras bigsbyi [see 1888, p.T66] as pene- 

 trating the siphuncular wall, and it has been suggested b}^ Owen [Pal. 1860,. 

 p. 85] that they served for the passage of blood vessels to the living 



Fig. 22 Actinoceras abnor- 

 m e Hall (sp.). Section showing the 

 endosiphuncle and tubuli. (Copy 

 from Zittel) 



