Cincinnati Society of Natural History. 



pentagonal anal plate ; succeeding the third radial is a fourth one, 

 which is about as long as wide, and is still included within the body ; 

 on the left side this piece articulates with the anal plate ; above the 

 body plates the rays are constricted, and in the right posterior, and 

 right anterior rays, there are four pieces in direct succession to the 

 base of the arms, the last one being an axillary piece; in the three re- 

 maining rays there are five pieces to the base of the arms. 



Arms ten, rather stout, long, rounded on the dorsal side, and com- 

 posed of pieces which in the largest examples studied are slightly wider 

 than long, and in young specimens, a little longer than wide; the fifth 

 piece in each arm is somewhat wedge shaped and slightly larger than 

 those below it, and supports on the upper lateral sloping side of its 

 thicker end, a small armlet; subsequently each succeeding fourth piece 

 throws off alternately on each side of the arms, a similar armlet ; at 

 the point of origin the width of the armlets is equal to about half of 

 that of the arms ; they seem to extend upward as far as the arms 

 themselves, and are composed of pieces that are nearly twice as long 

 as wide; usually every sixth or seventh piece is axillary, and supports 

 two equal divisions of the armlet. 



The single anal plate is pentagonal, and once and a half times as 

 large as the largest radial piece; it connects at the upper side with the 

 ventral prolongation, which extended some distance beyond the end of 

 the arms, and at intervals of about one eighth of an inch, or a little 

 more, is constricted so as to give it a beaded appearance ; and is com- 

 posed of numerous thin squamiform plates, that imbricate upward. 



Column of moderate size, pentagonal, and composed near the bod}' of 

 alternately thicker and thinner pieces; several inches below the body 

 the column becomes rounded, and the segments nearly equal. 



Dimensions of a medium-sized specimen: Length of body, .18 inch ; 

 breadth, .2 inch; length from last disk of column to base of arms, .34 

 inch; length of arms, about 1.5 inches; diameter of column .1 inch. 



Named in honor of the discoverer, Mr. George Oeh, whose collection 

 contains many fine specimens of Cincinnati crinoids. 



Formation and locality : On the hills back of Cincinnati, Ohio, at 

 an elevation of about 325 feet above low-water mark in the Ohio river. 



Heterocrinus pentagonus, n. sp. (Plate V., figs. 10, and 10a.) 



Body small, a little longer than wide, with the breadth but slightly 

 more above than below, in some specimens a little constricted above at 

 tha point where the rays become free; in old examples, pentalobate, 

 as seen from below, in consequence of each radial series being convex, 



