45 



specimen, but as many as thirty plates may be counted in a single 

 arm. Some of the arm plates bear a central spine or node, but 

 there is not uniformity in the different arms in this respect. 



This species is remarkable for its spines, nodes, and rough, un- 

 even, external surface, and is distinguished, by its structure and 

 the number of plates in the primary and secondary series, from 

 all other species. 



It was found in Clark county, Indiana, in what is called the 

 Knobstone, but which we think must be of the age of the Keokuk 

 Group, and is now in the collection of Wm. F. E. Gurley. 



Family DOLATOCKINID^. 



DOLATOCRINUS AMPLUS, n. sp. 



Plate IV, Fig. 6, basal view; Fig. 7, side view; Fig. 8, 

 summit view. 



Calyx large, subcylindrical or bowl-shaped, concave below. All 

 the plates are ventricose or subspinous and radiately furrowed 

 toward the margins. Our specimen is injured at the point of the 

 columnar attachment and part of the radial plates are destroyed. 



Basal plates not observed. First primary radials probably as 

 wide or wider than long. Second primary radials quadrangular, 

 a little wider than long. The calyx will rest on these plates and 

 the first interradials. Third primary radials larger than the sec- 

 ond, wider than high, pentagonal and bear upon each upper slopiing 

 side a single secondary radial. The secondary radials are axil- 

 lary and bear upon each upper sloping side four or five tertiary 

 radials. There are, therefore, four arms in each series or twenty 

 arm openings to the vault. 



The first interradials are the largest plates in the calyx. Four 

 of them have nine sides each, while the azygous plate has eleven 

 sides. In the regular areas the first plate separates the primary 

 and secondary radials and is broadly truncated on top for a sec- 

 ond plate that separates the secondary and first tertiary radials 

 and is slightly truncated on top by a small plate in the third 

 range, and this is followed by two small plates in the fourth 

 range which connect with small plates that separate the arms and 

 unite with the plates of the vault. The difference between tin- 

 azygous area and the other areas is very slight and consists in 



