596 THE CEINOIDEA CAMEEATA OF NORTH AJrEEICA. 



Physetocrinus asper <m. and w.). 

 Plate LXIII. Figs. 7a, b. 



1869. Stroiocriims {Fhijsetomnus) asper — Meek and Wokthen; Proceed. Acad. Nat. Sci. Piila., p. 181; 



also Geol. Rep. Illiaois, Vol. V., p. 351, Plate 7, Figs, la, b. 

 1881. Pkysetocrimis asper — W. and Sp. ; Revision Pateocr., Part II., 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 obliqiiely 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- 

 line from a donsal aspect. Eadials 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. 



EorivMi and Locality. — Upper Burlington limestone ; Burlington, Iowa. 



Type in the Museum of Comparative Zoology. 



Bemarks. — This species differs from all others of the genus in the form 

 of the calyx, and its style of ornamentation. 



