502 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



bulacral pieces, with occasionally a larger covering plate among them. 

 Interambulacral plates verj numerous and comparatively flat ; anal open- 

 ing lateral. 



Horizon and Locality — Keokuk group ; Indian creek, Montgomery Co., 

 Ind. 



Types in the collection of Wachsmuth and Springer. 



Remarks. — The specimen on Plate XXXIX., Fig. 7, is exceedingly inter- 

 esting as having on three of its arms well defined cysts, similar to those pro- 

 duced in recent Crinoids by Mt/sostoma, and it appears as if portions of the 

 parasites are still preserved on the fossil. This is the first instance where 

 such cysts have been noticed on the arms of Palaeozoic Crinoids. 



Agaricocrinus inflatus Hall. 

 Plate XLI. Figs, la, h, c, d. 



1801. Agaricocrinm injlatus — Hall; Prel. Des. New Pal. Toss., p. 4. 



1861. Agaricoerims {Amphoracrinus) iiiflatus — Hall;, Bost. Joum. Nat. Hist., Vol. VH., p. 281. 

 1S77. Ampkoracrinus infiaivs — S. A. Miller; Catal. Amer. Palasoz. Toss., p. 70. 



1881. Agaricocrinus injlatus — W. and Sp. ; Herisiou Palseocr., Part H., p. 112 (Proceed. Acad. Nat. Sci. 

 PMla., p. 286). 



A robust species, in form approaching Ampkoracrinus; the symmetry 

 extremely irregular. Calyx as high as wide and obscurelj' pentalobate ; the 

 interradial spaces at the arm regions slightly impressed. The whole lower 

 face of the calyx flat or concave ; the second interbrachials, the upper edges 

 of the first, and the arm facets the only pai'ts of the dorsal cup visible 

 in a side view. Ventral disk highly elevated, broad at the top, and enor- 

 mously inflated at the posterior side. The plates throughout the calyx 

 are but slightly convex, barely enough to bring out distinctly the suture 

 lines ; only the posterior oral is more or less nodose, and sometimes 

 subspinous. 



Basals hidden within the column concavity ; axial canal sharply pen- 

 tangular. Radials a little wider than long, the sides rapidly spreading, the 

 lower end thickened, forming a circular ridge around the columnar depres- 

 sion. First co?tals fully twice as wide as long, quadrangular, three of their 

 sides convex, the upper straight. Second costals wider, and sometimes longer 

 than the first, the sides spreading abruptl}^ Distichals 2X2; the plates 

 short and cuneate, meeting laterally with their pointed ends, their wider 

 faces directed to the outer sides of the rays, whereby the facets of the con- 

 fluent arms are brought into an even Hue ; contrary to the case of other 



