120 



THE CRINOIDEA 



between r. post. 11 and this proximal plate differs from that between 

 r. post. R & IBrj only in size (Fig. XXVIII.) ; in locrinus the 

 ventral groove of the median series coalesces in r. post. R with the 

 ventral groove of right posterior arm ; this, and other evidence 

 from Heterocrinidae, shows that the median anal series was in- 

 nervated from the axial cord of r. post. R. The only argument 



4. Scopliiocriwts elcyans. 5. Cyfithocriniwlongiinanu*, 6. Pnnsomnns. 



anal area. 



FIG. XXVI. 



Diagrams of the anal urea in various Inadunate Crinoids. (From Bather, after Waclisniiith 

 & Springer, Hall, and Angeliu.) 



against the view, is the improbability of a change of function in 

 the ramus ; still the view is not proven. 



A distinct question is whether the anal x, which frequently 

 occurs in the posterior interradius of the cup, is a secondary 

 element suddenly introduced, as are the anals of Camerata, or 

 whether it is the proximal median plate of the tube (as in locrinus, 

 Heterocrinidae, etc.), that has gradually sunk down into the cup. 

 Wachsmuth & Springer hold the former view, believing that 

 x is homologous with the strictly interradial anal of Camerata, 



