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096 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Physetocrinus asper (M. and W.). 
Plate LXIIL, Figs. 7a, b. 
1869. Strotoerinus (Physetocrinus) asper —MxEEK and WortHEen; Proceed. Acad. Nat. Sci. Phila., p. 181; 
also Geol. Rep. Illinois, Vol. V., p. 351, Plate 7, Figs. 1a, 6. 
1881. Physetocrinus asper — W. and Sp.; Revision Paleocr., Part IT., p. 157. 
Calyx moderately large, higher than wide. Dorsal cup obconical, with 
nearly straight sides, gradually expanding to the top of the distichals, the 
higher brachials curving obliquely outwards. Ventral. disk highly elevated, 
hemispherical, occupying fully one third the height of the calyx. Plates of 
the cup convex, covered with one or more rather large, angular protuber- 
ances of irregular form and size, some of them round, others elongate, and 
some transversely arranged, others longitudinally. 
Basal cup broad, nearly three times as wide as long, not thickened at the 
lower margin, deeply notched at the sutures, and presenting a trilobate out- 
ine from a dorsal aspect. Radials wider than long, and as large as the two 
costals together, which are of nearly equal size, and almost twice as wide as 
long. Arms ten to the ray, five from each subdivision; all free above the 
axillaries. Anal plate narrower than the radials, supporting ten or eleven - 
plates in five rows. The regular interbrachials consist of about eight pieces, 
which connect with the plates of the disk. Ventral disk inflated; composed 
of irregular, flat pieces of moderate size. Anus subcentral, at the top of 
a small protuberance. ‘Column small, round, the four or five proximal joints 
subequal. 
Hlorizon and Locality. — Upper Burlington limestone; Burlington, Iowa. 
Type in the Museum of Comparative Zodlogy. 
_ femarks. — This species differs from all others of the genus in the form 
of the calyx, and its style of ornamentation. 
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