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370 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Calyx somewhat biturbinate, as wide as high. The dorsal cup larger 
than the ventral disk; sides expanding gradually to the arm bases and 
forming nearly a straight line. Plates nodose, except the first costals which 
are generally flat. 
Base more than twice as wide as high, hexangular as seen from the 
bottom ; the interbasal suture lines distinctly grooved; column facet deeply 
depressed. Radials wider than long, widest at two thirds their height, exca- 
vated at the upper edges. Costals small, both together very little more 
than half the size of the radials; the first linear; the second a little longer 
and wider in the upper part. Distichals two, except in the divisions facing 
the anal side, in which there is but one, which is axillary. Palmars 2 X 20; 
but while those.approaching the posterior side bifurcate again, the others 
are followed directly by the free arms. Arm facets concave, arranged in 
a continuous row around the calyx. Arms twenty-two, short, almost of 
equal width to their tips. Pinnules closely packed together, long, deep, and 
flattened at the sides. Regular interbrachials consisting of one large plate, 
sometimes followed by one or two smaller ones; the former extending to 
the top of the first distichals and even tothe palmars. Anal plate consider- 
ably higher than the radials and succeeded by three large plates, and these 
by a single one. Ventral disk subconical, plates tuberculose, pointed at the 
top. Orals and first radial dome plates larger than the intervening supple- 
mentary pieces, which are quite irregular in form and size. Anal tube very 
long, sometimes extending several inches beyond the tips of the arms; com- 
posed of tumid plates. Column constructed of rather large joints with 
rounded edges; the internodals somewhat the narrowest. 
Fflorizon and Locality. — Lower Burlington limestone; Burlington, Iowa, 
and in rock of the same age in Southern Missouri. 
Type in the (Worthen) Illinois State collection, Springfield. 
Remarks. — There is not the least doubt that Actinocrinus discoideus and 
A. formosus, both described by Hall, are identical with this species. The 
former name has priority, but, being described from a crushed specimen, and 
neither the name nor the description giving a correct idea of the species, we 
are compelled to adopt McChesney’s name. The form described as Actino- 
crinus formosus differs only in the less convexity of the plates. 
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