506 THE CEINOIDEA CAMEEATA OF NORTH AJIERICA. 



Agaricocrinus bellatrema Hall. 

 Flate XLI. Figs. Jfu, h, c, d. 



1861. At/aricocrims oniolremn * — Hall; Prelim. Descr. New Palseoz, Toss., p. 3. 



1861. Agarkocrims (Ampkomcrinus) liellatrema — 'S.MA.; Bost. Joum. Nat. Hist., Vol. VII., p. 281. 



1877. Amphoracrims bellatrema — S. A. Millee ; CataL Amer. Palseoz. Foss., p. 70. 



1881. Agaricocrinus ornotrema — W. aud Sp. ; Eevision Palseocr., Part II., p. 112 (Proceed. Acad. Nat. 



Sci. Pliila., p. 286), and Whitfield, 1893, Mem. Am. Mus. Nat. Hist. N. York, Vol. 1., p. 24, 



Plate 2, Figs, 19, 22. 



Calyx subpyramidal in its anterior aspect ; the posterior side inflated and 

 strongly protruding ; the base completely flat or very slightly convex, and 

 distinctly pentangular in outline. 



Basals hidden by the column, the latter resting within a small concavity 

 formed by the lower margins of the radials; axial canal pentalobate. Radials 

 wider than long. The first costals smaller than the second and quadran- 

 gular ; the latter about twice as wide as long, pentangular, not larger than 

 the radials. Distichals 1X2; the plates cuneate, short, and followed by 

 two series of short arm plates. Arm facets very large, and those of the 

 same ray contiguous up to the third plate. Arms ten, quite heavy at the 

 base, but gradually tapering and ending in a sharp point. Pinnules long 

 and stout; their joints twice as long as wide. Pirst interbrachials the 

 largest plates of the calyx, and the only ones of the dorsal cup which some- 

 times are slightly convex ; subovate, reaching to one half the height of the 

 arm facets, and supporting two narrow pieces, which rise to a level with 

 the arm openings. First anal plate longer and generally narrower than the 

 radials ; the second anal somewhat smaller, the two interbrachials to each 

 side of the same form as the corresponding single plate of the other inter- 

 radii, but from a third to a half smaller. The next row consists of three 

 plates, of which the two outer ones, in part at least, are interambulacral. 

 The ventral disk at the posterior side bulges considerably upward and out- 

 ward, forming an inflation which, owing to its large size, disturbs consider- 

 ably the general symmetry. The median portion of this inflation, the part 

 containing the anus, consists of a subovoid, flattened area, which is directed 

 obliquely upward. The space is covered by small plates, and these in turn 

 are surrounded by eight or ten moderately large, strongly nodose or sub- 

 clavate pieces, a structure which gives to the anal area, and in fact to the 



* The name Agaricocrinus ornotrema was originally given to this species, but not being properly formed, 

 was afterwards changed by Hall to A. bellatrema. 



