13 



a slight depression along the sutures, giving the whole the appear- 

 ance of a small pouch, a little inflated in the middle, and contracted 

 at the top and the base of the arms, leaving no space except the anal 

 area, which is neatly filled with two or three anal plates, the lower 

 one the largest, pentangular, and forming a part of the calyx. Suture 

 lines of the body-plates not very distinctly defined. Surface smooth 

 or finely granulose. 



Locality and position, in the upper division of the Burlington Lime- 

 stone, Burlington, Iowa. — Collection of Rev. W. H. Barris. 



Zeacrinus sacculus var. concinnus. Another specimen, appar- 

 ently younger, from the same locality and position, presents no differ- 

 ences from the preceding species above the radials ; the subradials, 

 however, are only five, a little tumid, and proportionally smaller, mak- 

 ing the calyx a little lower ; the anal series also consists of one more 

 plate ; it is probable, however, that the quadrangular subradial of the 

 preceding species is of abnormal development, and that, were this 

 absent, the number of anal plates would be one more. 



Several specimens of a species of crinoid belonging to the family 

 of Cyathocrinidce have been discovered in the upper division of the 

 Burlington Limestone, at Burlington, which is so peculiar in its form 

 and structure, as to render its reference to any known genus quite 

 improper, for which I propose the generic name of Belemnocrinus. 



The following diagram and outline figure will show its structure 

 and form : — 



Fig. 1. 



Tig. 2. 



The dotted line shows the 



depth of the 



visceral cavity. 



Belemnocrinus typus. 



Belemnocrinus 



TYPUS. 



