Carboniferous Rocks of the Mississippi Vallct/. 289 



Summit and arms unknown. Articulating facet for the 

 attachment of the column very small, round. 



Surface of plates marked by strong, deep, angular pli- 

 cations, four on the anal plate, four on the anterior radial 

 plate, and three on each of the other radial plates ; these 

 plications commence at the small arm scar, and pass, one 

 to each lower lateral angle, and the others to the middle of 

 the lower margin ; one or two incipient plications occupy 

 the superior lateral portions of the radial plates. The pli- 

 cations on the basal plates radiate from the edge of the 

 column scar, and are there fourteen in number ; the six of 

 these which pass towards the sutures between the adjacent 

 radial plates bifurcate just before reaching the upper mar- 

 gin of the basal plates, the divisions uniting with those of 

 the lower lateral angles of the radial plates. On four of 

 the radial plates the plication which passes to the middle 

 of the lower margin unites with a single plication from the 

 basal plate, forming a continuous line from the arm scar to 

 the column ; while on the anterior radial and the anal plate, 

 where there are two plications to the lower lateral margin, 

 there are two direct plications on the basal plates parallel 

 to the suture lines. 



This species is closely allied to D. striatus, Owen, (Geol. 

 Surv. Iowa, Wisconsin, and Minnesota, pi. VA, fig. 10 ;) 

 but differs materially in the surface markings, being com- 

 posed of a much less number of stronger plications. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collections of Dr. O. Thieme 

 and C. A. White. 



Dichocrinus scitulus (n. s,). Body obconical, attenuated 

 below, with sides in nearly straight converging lines; 

 height about equal to or a little more than the greatest 

 width at the top of the radial plates. 



Basal plates a little swollen at the junction with the 

 column; equal in length to the radial plates. Radial 



JOURNAL B. S. N. H. 37 



