358 SMITHSONIAN INSTITUTION 



consideration the remaining species fall into two rather well marked sections, viz. : ( i ) those 

 without regular interbrachials, and (2) those which have them. In the first there are more 

 or less ample spaces between the rays and their divisions, but these spaces must have been 

 filled with perisome, as we actually find them in E. juglandiformis, where the small plates 

 become rather strong and are not far from the stage of interbrachials. In the second, distinct 

 interbrachials appear to a limited extent, but they never become so important as in some of 

 the true Taxocrini. As a rule the anal interradius is narrow and the tube small, notable 

 exceptions being E. juglandiformis and E. perplexus. Sixteen species are recognized, one 

 from the Silurian, thirteen from the Devonian, and two from the base of the Lower Car- 

 boniferous, which may be arranged as indicated below. Of the other species described under 

 Taxocrinu s but resembling this genus in having two IBr, T. rigens Angelin is a synonym; 

 T. priscus Steininger and T. gracilis Meek and Worthen are insufficiently defined ; and 

 T. grebei Follmann probably does not belong to the Flexibilia. 



The Species of Eutaxocrinus 

 I. Arms long, branching very unequally, with strongly modified dichotomy. 



iBr few and small. 



IIBr 3 E. oblongatus. 



II. Arms branching with ordinary dichotomy. 

 No iBr. 

 IIBr 4. 



Crown short, turbinate. 



Arms broad and short, tapering rapidly. 



Surface tubercular E. rhenanus. 



Crown elongate. 



Arms stout, tapering gradually. 



Surface smooth E. stuertzii. 



Crown elongate, cylindrical. 



Arms long, slender, tapering gradually. 



Anal interradius very narrow ; iBr may occur (?)■£• pulcher. 



IIBr 3 or 4 irregularly. 

 Crown elongate, turbinate. 



Margins of Br not raised E. ithacensis. 



Crown short, rotund. 



Specimens very small E. alpha. 



Specimens medium to large size E. curtus. 



IIBr usually 3. 



Crown elongate, turbinate. 



Margins of Br raised E. zvhiteavesi. 



Crown elongate, broad and rotund below. 



Rays angular dorsally. iBr spaces narrow E. eifelensis. 



Rays not angular. iBr spaces wide. 



Anal tube wide, composed of very short plates. 



RR largest plates in calyx. E. juglandiformis. 



