224 



ECHINODERMATA— PELMATOZOA 



PHYLüM IV 



alternating sides bearing stout pinnules which are well separated, resembling 

 ramules. Ventral sac large, often almost as long as the arms. Stern rela- 

 tively small, sub-pentagonal, with rather plentiful cirri. Devonian and 

 Lower Carboniferous (Keokuk) ; North America and Europe. 



■ Aulocrinus W. and Sp. Like the preceding, but ventral sac forked, with 

 anal opening from a lateral spout. Stern sharply pentagonal, with cirri. 

 Keokuk Limestone ; Indiana. 



Scytalocrinus W. and Sp. Similar to Decadocrinus, but with calyx usually 

 elongate, more or less conical base, arms cylindrical, and pinnules closely 

 packed. Stem large, round, with cirri sparse and mostly distal. Devonian 

 and Carboniferous (Goal Measures) ; North America and Europe. 



Agassizocrinus Shumard ex Troost MS. {Astylocrinus Roemer) (Fig. 325). 



Calyx elongate, ovoid to pyriform. Arms ten, with pinnules closely packed, 



a as in Scytalocrinus ; brachials quadrangular, becoming 



cuneiform distally. Ventral sac unknown. Infrabasals 



five, in mature specimens fusing to a rounded undivided 



base. Stem entirely wanting, but probably present in 



early stages. • Carboniferous (Kaskaskia to Coal Measures) 



Mississippian area ; North America. 



Cromyocrinus Trautsch. (Figs. 326, 

 327). Calyx rounded below, but not 

 concave. IB large, visible exteriorly. 

 Arms five, or ten, stout, not branching 

 beyond the first axillary. Brachials 

 quadrangular to cuneiform, tending to 

 become biserial. Ventral sac incon- 

 spicuous. Stem round. Lower Car- 

 boniferous ; Eussia and Mississippi 

 Valley area. 



Ulocrinus Miller and Curley. Similar 

 to Cromyocrinus, but with anal x entirely 

 above the radials ; that is, 

 with radianal but no anal 

 in the dorsal cup. Arms 

 unknown. Upper Carbon- 

 iferous ; North America. 



Eupachycrinus Meek 

 and Worthen. Similar to 

 Cromyocrinus, but calyx 

 low, rounded, with concave 

 base ; infrabasals at bot- 

 tom of a funnel. Arms ten to twenty. Brachials quadrangular to biserial. 

 Stem round, with. cirri. Kaskaskia to Upper Carboniferous ; North America 

 and Europe. 



Tribrachiocrinus M'Coy (Pentadia Dana). Calyx globose. Infrabasals three, 

 large. Radials irregulär in size and form, apparently only three arm-bearing. 

 Arms unknown. Permo-Carboniferous ; Australia. 



Fig. 326. 



Cromyocrinus globulus 

 M. and W. Lower Car- 

 boniferous ; ehester, 111. 

 Natural size (after Meek 

 and Worthen). 



Fig. 325. 



Agassizocrinus laevis 

 (Roemer). Kaskaskia 



Group ; Illinois, a, Com- 

 plete crown, after Roe- 

 mer in Bronn, soniewhat 

 restored ; b, Ventral as- 

 pect of the coalesced 

 infrabasal disk ; c, Side- 

 view of same, nat. size 

 (after M. and W.) 



t>^. 



Fig. 327. 



Analysis of plates in the dorsal cup of 

 Cromyocrinus. ib, Infrabasals ; b, Basais ; 

 r, Radials ; ra, Radianal ; a, a', a", Anal 

 and lower tube plates (after Bather). 



