FOSSILS OF THE BUKLDs'GTOX GROUP. 433 



the first radial on the left. Above these the others extend 

 up to connect with the proboscis (so called.) 



Anns all distinctly rounded, and after their origin on the 

 second radial pieces each bifurcating first on the fifth, sixth, 

 seventh or eighth piece, above which the outer division 

 bifurcates (or gives off an arm on the inner side) twice or 

 three times at more or less nearly equal distances, all the 

 inner arms continuing simple throughout their entire 

 length, and equaling the outer divisions in thickness. Arm 

 pieces short and very distinctly wedge-formed, each having 

 a moderately stout tentacle at its larger end, along the 

 inner lateral margins of the arms: axillary or bifurcating 

 pieces a little larger than the others, but not more convex. 

 Tentacles composed of joints about twice as long as wide. 



Body plates not convex, and merely separated by linear 

 sutures, which are not gaping even between the first and 

 second radials; entire surface more or less granular. 



Hight of body to top of first radials, about 0.25 inch; 

 breadth, about 0.50 inch; length of arms, apparently nearly 

 '2 inch" 



This species is related to Poteriocrinu* bursceformis, of White, which 

 has its body formed exactly as in Poteriocrinw, with its arms and 

 primary radials presenting all the characters of ZeomatM, as was 

 noticed by Dr. "WHITE ; thus showing, with the species under consid- 

 eration and some others, that Zeacrinus can scarcely be regarded as 

 more than a subgenus under Poterioerinites. The form that we have 

 here described differs, however, specifically from Dr. WHITE'S species, 

 in having its body proportionally shorter and smaller. Its arms also 

 differ in being very distinctly rounded, instead of flat, while its anterior 

 ray supports two arms directly on the second radial piece, as in all the 

 other rays, instead of having the first bifurcation in that ray on the 

 fourth piece. 



The specimens are not in a condition to show much of the ventral pro- 

 longation, but one of them shows that it is verynearly as long as the 

 arms, and somewhat expanded and crowned with short spines at the 

 upper extremity. 



l,"<;tlity and 2>oxition Upper division of the Burlington group, at 

 Burlington, Iowa. Lower Carboniferous. Xo. 319 of Mr. WACHS:MITTH'S 

 collection. 



