342 SMITHSONIAN INSTITUTION 



Suborder TAXOCRINOIDEA 



Family TAXOCRINIDAE Wachsmuth emend. Springer 



Taxocrinoidea with posterior interradius always differentiated and occupied by 

 anal plates in a tube-like series, none of which are incorporated in the calyx. 



All ANAL PLATES FROM POSTERIOR BASAL UP SEPARATED BY PERISOME FROM ADJACENT 



brachials at one or both sides. dlstal face of posterior basal not suturally 

 connected with anal plate. rays above radials partly or wholly separated all 

 around. Crown usually elongate. 



Analysis of the Genera 



I. RA in lower positions. 

 Arms dichotomous. 



Rays wholly separated by iBr or perisome. 

 RA in form of R, under r. post. R. 



iBr few. IBr 2 Protaxocrinus. 



RA rhombic, obliquely to lower left of r. post. R. 



iBr few. IBr 2 or 3 Gnorimocrinus. 



II. RA, if present, only in upper oblique position. 

 Arms dichotomous. 



Rays wholly separated by iBr or perisome. 



iBr variable, usually few. IBr 2 Eutaxocrinus. 



iBr frequently numerous. IBr 3 Taxocrinus. 



Rays abutting above iBr. IBr 3 Parichthyocrinus. 



Arms heterotomous. 



10 main trunks with ramules. IBr 3 to 6 Onychocrinus. 



