23 



More than half of the vault is preserved in our specimen. It 

 is elevated over the arm openings and gently convex centrally. 

 The plates are polygonal, the smaller ones convex, and the 

 larger ones nodose. The central plate is nodose, and surrounded 

 by seven plates. The plates are preserved from the central 

 plate to the middle of the azygous area and there are no indica- 

 tions of an orifice or proboscis. Evidently there is no proboscis, 

 in the species, and if an orifice, it was. in our specimen, out of 

 the normal position. No ovarian pores are visible. 



This is a peculiar species so different in form and all specific 

 characters from others that no comparison is necessary to be 

 made with any of them. 



Found by C. S. Hodgson, in the Burlington Group, in Adams 

 county Illinois, and now in the collection of S. A. Miller. 



AGARICOCRINUS HODGSONI, n. Sp. 



Plate I, Fig. 17, basal view; Fig. 18, summit view; Fig. 19, 

 azygous side view; Fig. 20, view ojrposife the azygous area. 



Species robust and medium or above medium size. Calyx 

 slightly convex in the lower part, but depressed in the region 

 of the third radials. Outline ovate. Plates thick, more or less 

 convex, and part of them subspinous. Arm openings directed 

 below a horizontal line. 



Basals form an hexagonal disc about one-half wider than the 

 diameter of the column, that contains a moderately concave 

 depression, radiately lined near the margin for the attachment 

 of the column. The columnar canal is small and cinquefoil. 

 The first primary radials are the largest plates in the calyx, a 

 little wider than long, three hexagonal, two heptagonal. All 

 of them are sculptured, so as to be pyramidal, the apices ex- 

 tending below the basals so that a specimen laid upon a table 

 will rest upon these plates and the point of the first azygous 

 plate. Second primary radials, quadrangular, transversely 

 convex, about three times as wide as long. Third primary 

 radials very little, if any, larger than the second, transversely 

 convex, pentagonal, axillary, and, in three of the rays, sup- 

 port on each upper sloping side two secondary radials, which 

 gives to each of these rays two arms. On the distal side of 

 each third primary radial adjoining the azygous area there are 

 two secondary radials, and on the proximal side a single sec- 

 ondary radial, which is axillary and supports upon the distal 

 superior sloping side a single tertiary radial, and on the prox? 



