CONTRIBUTIONS ON THE OCTOCORALLIA — BAYER 219 



lines of evolution. The isidids could have arisen from articulate 

 scleraxonians by elimination of the spicules from the horny axis seg- 

 ments. Extending this theory, it is possible that the ellisellids arose 

 from ancestral isidids by elimination of the horny nodes. That such 

 an evolutionary trend actually existed is intimated by Moltkia, an 

 articulated form (Isididae? I have not examined its axis structure) 

 from the Danian formations of northern Europe, in which the horny 

 nodes are overgrown by the calcareous internodes and the axis articu- 

 lation is consequently obliterated. 



The phylogenetic significance of the similarity of axis structure of 

 the Pennatulacea and the ellisellid gorgonians remains to be deter- 

 mined. It seems to speak as strongly for the origin of the Penna- 

 tulacea from gorgonacean ancestors as other features do for its descent 

 from alcyonacean stock. However, the Pennatulacea seems to be a 

 very old group, antedating any known Gorgonacea. 



References 



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 Duncan, P. Martin 



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