CLASS in CRINOIDEA 195 



(?) Beyrichocrinus Waag. and Jahn. Silurian ; Bohemia. 



Gennaeacrinus W. and Sp. Basais three. Calyx low and broad, strongly 

 lobed at the arm bases ; plates thin and highly ornamented. First primibrach 

 hexagonal ; iBr rather numerous. Arm openings twenty-five or more ; arms 

 unknown. Devonian ; Indiana and New York. 



Megistocrinus Owen and Shum. {Tylocrinus Wood). Basais three. Calyx 

 usually large, hemispheric, with greatest height below the arm bases ; usually 

 biit little lobed ; plates heavy, smooth or ornamented. Interbrachials 

 numerous ; first primibrach hexagonal. Arms sixteen to twenty, branching 

 in the free State, biserial above and below the bifurcations. Devonian to 

 Lower Carboniferous (Upper Burlington) ; North America. 



Subfamily B. Barrandeocrininae. 



Tegmen narrow and rigid. Arms permanently directed downward enclosing the 



mlyx. 



A highly specialised type, represented by a single genus, which, though having a siniilar 

 calyx, ditfers so strongly in habitus from those of the next section that it is better kept 

 separate. 



Barrandeocrinus Angelin (Cylicocrinus S. A. Miller). Basais three. Calyx 

 rather elongate, with tegmen nearly flat. Interbrachials few, definitely 

 arranged. Arms ten, heavy, biserial, directed downward over the calyx, with 

 pinnules opening outward. Silurian ; Gotland and North America. 



Subfamily C. Batocrininae. 



Tegmen hroad, well differentiated ; 'plaies large atid heavy, forming a rigid roof. 

 Arms not branching heyond the calyx; biserial. Respiratory por es fr equently present. 

 First primibrach (costal) usually quadrangular. Basais three in all known genera. 

 Devonian to Lower Carboniferous. 



This section flourishes araid a remarkable local development of Crinoid life especially 

 characteristic of the Mississippian area of the United States. The fauna is enormously prolific 

 in numbers and variety in the Burlington and Keokuk limestones of the Mississippi Valley, but 

 alniost entirely wanting in the Lower Carboniferous of Great Britaiu and Belgiuni, and of 

 other parts of the United States. Only a few straggling species come from the Devonian. 



§ 1. Anus at the end of a tube. 



a. Interbrachials few, separated from tegmen by arch of brachials. 



Batocrinus Casseday. Calyx biturbinate. Arms short, equidistant. Anal 

 tube very long, central, extending beyond arms. Kinderhook to St. Louis 

 Group; North America. 



Eretmocrinus Lyon and Cass. Like Batocrinus, but arms paddle-shaped, 

 and anal tube short, eccentric, tending to curve. Devonian to Keokuk 

 Group ; North America. 



Alloprosallocrinus Lyon and Cass. Calyx conical ; dorsal cup almost flat, 

 greatest height above the arm bases. First primibrach usually wanting. 

 Approaching Agaricocrinus in shape. Anal tube sub-central ; arms unknown. 

 Keokuk limestone ; North America. 



ß. Interbrachials few, usually separated from the tegmen except at anal skle. 



Macrocrinus W. and Sp. Calyx elongate, biturbinate to subovoid. Anal 



