78 



ORGANIC DEPENDENCE AND DISEASE 



parasitism continued. The habit was extinct; I think we 

 may say that this particular adjustment had been extin- 

 guished. 



SYMBIOTIC CONJUNCTION OF CRINOIDS AND 

 STARFISHES 



This is a habitude which, so far as known, is exhibited 

 only in the Mississippian fauna of the Lower Carbonifer- 

 ous and on its face it would appear to be a purely voluntary 

 association, as there is no anatomical evidence that the star- 

 fish has sacrificed its locomotive 

 function and none that the adjust- 

 ment is essentially unlike the associa- 

 tion between Glyptocrinus and Cy- 

 clonema. The known facts regarding 

 the combination are interesting. The 

 starfish is Onychaster flexilis Meek 

 and Worthen; it has rarely been 

 found undetached. The crinoid 

 seems most commonly to have been 

 the high-domed species Actinocri- 

 nus multiramosus. Wachsmuth and 

 Springer^ tell of finding forty speci- 

 mens of this crinoid in the Craw- 

 fordsville shales of Indiana, of which 

 nearly one-half had the attached 

 starfish, and these authors were 

 strongly disposed to the view that, 

 because of the elevation of the anal 

 tube and the situation of the waste 

 aperture near its apex in a position seldom if ever cov- 

 ered by the mouth of the starfish, the association was one 

 of comfortable attachment only. Reference is made by 

 the same writers to the fact that this starfish at the locali- 



11897, "N. Amer. Crinoidea Camerata," p. 566. 



Fig 65. The crinoid Acti- 

 nocrinus multiramosus with 

 a starfish (Onychaster) 

 attached to the anal tube. 

 (After Wachsmuth and 

 Spi'inger. ) 



