35 



twice as large as the subradials, about twice as wide as high, 

 pentagonal, truncated the entire width above, convex towai'd 

 the superior central part, and separated externally from the 

 second radials by a gaping suture. Second radials larger than 

 the first, twice or more than twice as wide as high, longitud- 

 inally angular in the central part, pentagonal, and in three of 

 tlie rays support upon each upper sloping side a robust arm. In 

 the ray adjoining the azygous area, on the right, the distal side 

 of the second radial bears a single arm and the proximal side 

 bears a secondary radial, which is axillary, and supiiorts ujion 

 eich upper sloping side a free arm; and the ray adjoining tlie 

 a'.ygous area on the left, beai's, on the ijroximal side of the 

 second radial, a single arm, and on the distal side a secondary 

 radial that is axillary, and supjjorts an arm on each upper 

 sloping side, which ari'angement gives to each of these rays 

 three arms, There are, therefore, twelve arms in this species 



The arms are robust, and in the lower pait composed of 

 quadrangular plates with transverse sutures, which graduate 

 into cuneiform plates in the ujjward extension of the arms. Each 

 plate supi^orts upon the thicker end a coarse, strong pinnule, 

 and in the middle jiart a small node, which form a j-ow of 

 nodes on each arm, that gives it a somewhat rough aspect. 



There is only one azygous plate. It truncates the larger 

 subradial, separates the fiist radials but does not extend as 

 high as the second radials, which unite over the toji of it. 

 The single azygous plate is. therefore, enclosed within the side 

 of the calyx in the same manner that it is in Graphiocrinns. 



If this species had no subradials, we would refer it to 

 Graphiocrinns, notwithstanding it has twelve arms; but as no 

 species having subradials can be congeneric with one not hav- 

 ing them, we have no hesitation in saying, that it is not a 

 Grapliiocrinu!>. And here we may say, that after having ex- 

 amined definitions and illustrations of all the species found in 

 this couulry, that have been referred to Graphiocrivus, by 

 different authors, we are fully convinced that the genus has 

 not been found in America. 



When Prof. James Hall founded the genus Scaphiocrt^ms. 

 in the Geology of Iowa, Vol. I. p. ."'il, and described the type, 

 Scaphiocrinus siinjilcx, lie very clearly distinguished it from 



