Carboniferous Rocks of the Mississippi Vallet/. 291 



above, and the strong ridges and intermediate nodes, are 

 sulliciently distinctive. 



Geological formation and locality. Burlington lime- 

 stone, Bm-lington, Iowa. Collection of C. A. White. 



Dichocrimis pocil/um (n. s.). Calyx goblet shaped, 

 height and width about equal, or width a little the greater. 

 Basal plates somewhat more than one third the entire 

 height, very slightly protruded at the junction with the 

 column. Radial plates sub-quadrangular, wider above 

 than below; the postero-lateral rays narrower than the 

 others, the proportion of length and breadth about one 

 and a half to one. Anal plate wider than the other plates, 

 and longer than the postero-lateral rays. The articulating 

 scar on the upper margin occupies a little more than one 

 third the width of the plate, semi-oval, slightly indenting 

 the face of the plate, and margined by a thick rim. 



The base of one of the arms which remains shows a 

 short, wide, quadrangular plate, with a second short, wide, 

 pentagonal plate anchylosed with the first ; and upon the 

 upper sloping sides of this rest the small arm plates. Col- 

 umn round at its junction with the body. Surface granu- 

 lose or striato-granulose. 



A specimen, which appears to be the young of this spe- 

 cies, has a length from the column facet to the top of the 

 dome of -f,f,^ of an inch ; and to the top of the radial 

 plates of -^2jl_ of an inch ; with a width at the top of the 

 radial plates of -f^^ of an inch ; giving to the fossil, when 

 deprived of its arms, an ovoid form. 



The dome consists of few plates ; one between the 

 bases of the arms is larger, while on the anal side there 

 are numerous small plates with a minute opening, and the 

 whole are crowned at the summit by a plate much larger 

 than any of those below. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of C. A. White. 



