196 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



tube rather large, extending beyond arms. Arms twelve to sixteen. Upper 

 Burlington and Keokuk Gr. ; America. 



Dizygocrinus W. and Sp. Calyx rotundate. Anal tube rather small, 

 usually not extending beyond the arms. Arms single or double, from twelve 

 to twenty openings. Upper Burlington to St. Louis Group ; America. 



Eutrochocrinus W. and Sp. Calyx wheel-shaped. Anal tube long. Arms 

 short, eitber single or double from twenty openings. Upper Burlington and 

 Keokuk Group ; America. 



y. Interbrachials few, sometimes connected with tegmen all around. 



Uperocrinus Meek and Worthen (Lohocrinus W. and Sp., Hyperocrinus 

 Bather) (Fig. 297). Calyx pyriform. Anal tube large 

 and often spiniferous. Arms short, single, often arranged 

 in groups, openings directed upward. Upper Burlington 

 and Keokuk ; America. 



§ 2. Anus without a tube, directly through tegmen. 

 Interbrachials few, usually not connecting with tegmen except 

 at anal side. 



Aorocrinus W. and Sp. Calyx small, elongate to ro- 



tund or biturbinate. Arms 

 rather strong, onefrom each 

 opening, cylindrical. Teg- 

 men plates not spiniferous. 

 Devonian to Burlington ; 

 Europe and America. 



Coelocrinus M. land W. 

 (Sphaerocrinus M. and W. 

 non Roemer). Similar to 

 preceding genus, but with 

 concave base. Burlington 

 Group ; America. 



Dorycrinus Roemer (Fig. 

 298). Calyx small to'large; 

 posterior oral alone, or with 

 primary radial plates of 

 tegmen, spiniferous. Arms 



rather small, usually two from each opening. Devonian to Keokuk ; America. 

 Agaricocrinus Hall (ex Troost). Calyx small to large, hemispherical, with 



dorsal side usually flat or concave, and greatest height above the arm bases. 



First primibrach sometimes hexagonal. Arms ten to sixteen, very heavy, 



directed outwards. Burlington to Keokuk ; America. 



Fig. 297. 



Uperocrinus pyriformis 

 (Shumard). Lower Carbon - 

 iferous ; Burlington, Iowa. 

 Nat. size (after Meek and 

 Worthen). 



Fig. 298. 



Dorycrinus quinquelohus (Hall) 

 var. intermedius(M. and W.). Lower 

 Carboniferous ; Burlington, Iowa. 

 Calyx viewed from the anal side. 

 Natural size (after Meek and Wor- 

 then). 



Family 8. Actinocrinidae. 



Monocyclic. Lower brachials, with well-defined interbrachials between them, 

 forming an important part of the dorsal cup. Radiais in contact except at the anal 

 side, where they are separated by a hexagonal anal plate, followed by two plates in the 

 second ränge. Basais three, forming a hexagon. Arms biserial in all known genera. 

 Rays usually branching by alternate bifurcations. Lower Carboniferous. Kinder- 

 hook to Keokuk. 



