CLASS III CRINOIDEA 205 



Silurian ; Gotland. Silurian to Devonian (Niagara, Manlius, Helderbergian) ; 

 North America. 



Metichthyocrinus Springer. No RA. No anal ; posterior basal not differ- 

 entiated. Crown rotund. Arms dichotomous, interlocking and infolding. 

 IBr two. Type, Ichthyocr. tiaraeformis Hall ex Troost MS. Lower Carbon- 

 iferous (Kinderhook to Lower Burlington) ; Mississippian area ; North 

 America. 



b. Rays above radials partly or wholly separated all around ; posterior radials separated 

 by anal x when present, 



Euryocrinus Phillips. No RA. Arms dichotomous. Anal x followed by 

 others in a single series. iBr few, usually in single series. IBr three. Lower 

 Carboniferous ; England. Devonian to Lower Burlington ; North America. 



Amphicrinus Springer. Similar to Euryocrinus, but with iBr numerous, in 

 more than one series, and primibrachs two. Lower Carboniferous ; Scotland. 



Dadylocrinus Quenst. (Dimerocrinus Pacht non Phillips). No RA. Crown 

 elongate, expanding from RR up. Arms heterotomous, with twenty main 

 trunks bearing ramules. iBr few or absent. Anal x followed by others in 

 more than one series, suturally connected at the sides. IBr two. Devonian ; 

 Russia, Belgium. 



Synerocrinus Jaekel {Forbesiocrinus Trautschold non de Kon.). Similar to 

 Dadylocrinus, but with anal x followed by others in series tending to form a 

 tube (transition toward Taxocrinidae). Crown more rotund in young 

 individuals. Lower Carboniferous ; Bergkalk near Moscow, Russia. 



Wachsmutliicrinus Springer. Similar to Dadylocrinus, but with no anal 

 plate, posterior basal not difFerentiated. The last survivor of this family in 

 America. Type, Forbesiocrinus thiemei Hall. Lower Carboniferous, Kinder- 

 hook to Upper Burlington ; Mississippian area ; North America. 



B. AU anal plates sejparated by perisome from adjacent brachials at one or both 

 sides, tending to form a tubulär series, from posterior basal up. 



Suborder 2. TAXOCRINOIDEA. 



Family 4. Taxocrinidae Bather emend. Springer. 



Infrabasals usually abutting on dorsal side of basals, but low, taking Utile part 

 in the calyx wall. Crown usually elongate, with arms divergent, and not abutting 

 above interbrachial areas. Interbrachials present all around. Ordovician to Lower 

 Carboniferous. 



Protaxocrinus Springer (Taxocrinus Ang. pars ; Lecanocrinus Billings). Arms 

 dichotomous. RA in form of R, below r.post.R. iBr few. IBr two. Type, 

 Taxocrinus ovalis Ang. Ordovician to Silurian; Gotland, Canada and the 

 United States. The geologically earliest known genus of the Flexibilia. 



Gnorimocrinus W. and Sp. (Taxocrinus Ang. pars). RA rhombic, obliquely 

 below r.post.R. iBr few. IBr two (or three). Type, Taxocrinus expansus 

 Ang. Silurian; Gotland and North America, western Niagara area. (?) 

 Devonian ; Belgium. 



Eutaxocrinus Springer. No RA. iBr variable. IBr two. Type, Taxo- 

 crinus affinis Müller. Silurian and Devonian to basal j^art of Lower Carboni- 

 ferous (Kinderhook) ; Gotland, Germany, North America. 



