No. 514] ARTICULATIONS OF CBINOIDS 587 



old as the phylogenetically much more primitive straight 

 muscular articulation between the radial and tin* first 

 postradial joint, and ontologieally older than tlie si might 

 muscular articulation succeeding it. Neil her can wc 

 hope for any Jight when we know the embryology of Hie 

 Pentacrinitida 1 , for the early stages of the IVntacrinitida' 

 are undoubtedly practically the same as those of the 

 comatulids, the only tangible difference in the adults 

 being an enormous increase in the number of the short 

 discoidal joints occurring at the top of the Antcdon stem, 

 and (of secondary importance) the retention of the stem. 

 I have only been able to examine a very few fossils in 

 regard to the interbrachial articulations; the results of 

 my study of Vintacrinus have already been published; 

 Pentacrinites (" Extracrinus") is exactly like Isocrinus 

 (restricted, i. e., excluding Endoxocrinus) except for the 

 small detail of the heterotomous instead of dichotomous 

 condition of the extraneous division series, and Mar- 

 ■ supites is exactly like Antcdon, even in the position of 

 the proximal syzygies; but I am convinced that a detailed 

 and careful study of the articulations and articular faces 

 of the joints in the fossil crinoids is one of the best lines 

 of procedure in the elucidation of their systematic 

 relations. 



