86 Cificiiinaii Society of Natural History. 



Our specimen must be much better preserved than his, as 

 it shows much more than his did. The iml:)ricating plates, of 

 course, are simply the reverse of the opposite side. It is in 

 the arms and central part that we note important structural 

 discoveries. The under side of the rays, as seen from below, 

 consist of a row of plates on each side of the furrow, which 

 interlock at the bottom of the furrow, and are, therefore, 

 without reference to abutting imbricating plates, pentagonal 

 instead of quadrangular, as Meek described them. They 

 extend beyond the margin of the imbricating plates into the 

 visceral cavity, half the depth of the ambulacral furrows, and 

 are separated from each other, in their extension laterally into 

 the visceral cavity, so as to present a strongly serrated edge, 

 as shown in the illustration. The furrows are covered with 

 thin non-imbricating plates, that do not cover the serrated 

 edges above described. Part of the covering is preserved in 

 our specimen, as shown in the illustration, on two rays, but 

 the plates are so small and the sutures so indistinct, that they 

 could not be shown, except in a greatly magnified view. The 

 coverings of the rays are united near the center of the fossil 

 by a subpentagonal rim, that extends deeper into the visceral 

 cavity than any part of the internal rays, and, we believe, 

 extended to the very bottom of the test, and formed the part 

 of the organism that adhered to the foreign object to which 

 these animals attached. Three sides of this projecting rim 

 are preserved and shown in the illustration, and the surface is 

 flattened, as if for the purpose of attachment. Within this 

 pentagonal rim there is a pit showing the five subovate 

 mouths of the amljulacral canals, which are also indicated in 

 the illustration. 



This internal framework of Agelacrinus, we believe, has 

 never before been illustrated or described. We regret that 

 the side of the central pit, on which the anal opening is 

 situated, and the internal part of that orifice, are destroyed in 

 our specimen; for it would be very interesting to know 

 whether or not the two were connected, and, if so, in what way. 



The specimen illustrated was found near the top of the 

 hills, in Cincinnati, in the Hudson River Group, and belongs 

 to Mr. Faber. 



