69 



There is no described species, from rocks of the same age, 

 with which this one can be confounded. 



Found by the distinguished collector and naturalist F. A. 

 Sampson, in the Choutean limestone at Sedalia, Missouri, and 

 now in the collection of S. A. Miller, to whom he kindly pre- 

 sented it. 



CYATHOCRINUS MACADAMSI, n. Sp. 



Plate IV, Fig. 31, azygous side on the right; Fig. 32, lateral 



view. 



Species medium size, constricted above the calyx. Calyx 

 short, hemispherical, twice as wide as high; plates convex; 

 sutures distinct; surface finely granular. Column small. 



Basals form a flat pentagonal disc about twice as wide as 

 the diameter of the column. Subradials slightly wider than 

 high and forming with the basals a low cup. First radials 

 about one-half wider than long, pentagonal, truncated the en- 

 tire width above, and separated from the second radials or 

 brachials by a wide gaping suture. There are two brachials 

 in each ray, the first one is quadrangular and about twice as 

 wide as long, the second is somewhat smaller than the first, 

 pentagonal, axillary and supports upon each upper sloping side 

 a single arm. The body is broadly constricted in the region 

 of the brachials. There are only ten arms and when closed 

 they are compact, as the sides are straight and flattened. The 

 arms are composed of wedge-shaped plates, the first ones be- 

 ing longer than the succeeding ones. In the three specimens 

 examined there is some difference in the length of the arm 

 plates and the longer ones appear to be slightly constricted, 

 but the difference will not distinguish either specifically from 

 the one illustrated. The first azygous plate truncates a sub- 

 radial and extends a little above the top of the first radials. 



The form of the calyx and the azygous plate agree with 

 Cyathocrinus, but the brachials and arms remind one of Poterio- 

 crinus and Zeacrinus. There is no described species for which 

 this one can be mistaken. 



Found by the late Hon. Wm. Mc Adams, in the St. Louis Group, 

 at Alton, Illinois, and now in the collection of S. A. Miller. The 

 specific name is in honor of the collector, who was well 

 known as a naturalist of ability and close observation for many 

 years. 



