11 



This species not only resembles Zeacrinus above the base, but 

 possesses those characters which have been regarded as peculiar to 

 that genus, of having but two radials to four of the rays, and a 

 greater number to the anterior one, yet the body has the true form 

 and development of Poteriocrinns. 



From P. cahjciilus, Hall, it differs in the peculiarity of the radials 

 just mentioned, and the proportions of the body-plates. From P. 

 lepidus, Hall, it differs in having a less number and less massive 

 radials, and being without the distinctly marked suture-lines and the 

 depressions of the angles of the body-plates which that species has. 



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

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



Genus Buesacrinus Meek and Worthen. 



BuRSACRiNUS CONFIRMATUS (n. s.) Body rather rapidly spreading 

 to the top of the second radials, which are prominent, and pointed at 

 their upper extremities, giving the body at this point a stellate outline 

 when viewed from below. Basal plates unknown ; subradials small, 

 about as wide as high ; first radials nearly twice as wide as high, the 

 lower angle made somewhat acute by the slight concavity of the 

 lower sides ; upper margins broadly concave, or nearly straight ; 

 second radials rather larger than the first, the lower sides slightly 

 convex, the upper sides sloping with an obtuse angle, which is made 

 to appear more acute than it really is, by the forementioned projec- 

 tions ; arm-plates about twice as wide as high, convex transversely, 

 leaving a distinct depression of the arm-sutures, and having a small 

 angular prominence at the middle of their upper sides. 



The only known specimen of this species was in the cabinet of the 

 writer two years before the publication of the genus to which it is 

 now referred. It was known to possess new generic characters, but 

 the specimen was thought too imperfect to found a new genus upon ; 

 yet it affords specific characters which cannot be mistaken, and is 

 referred without doubt, and with much satisfaction, to the genus Bur- 

 sacrinus of Messrs. Meek and Worthen, since it conforms to and fully 

 confirms that genus, which was founded upon a single specimen. 



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

 stone, Burlington, Iowa. 



Genus Zeacrinus Troost. 

 Zeacrinus perangulatus (n. s.) Calyx more than twice as wide 

 as high, base rather broad, deeply excavated ; basal plates very small, 

 covered by the column, which is not large, round, and composed of 

 thin, alternating joints ; subradials of medium size, about as wide as 

 high ; first radials the largest, plates of the calyx wider than high ; 

 second radials a little larger than the first, pentagonal, and support- 

 ing each a pair of arms, except the anterior one, which is quadran- 



