110 Cincinnati Society of Natural History. 



The first radial on the left of the azygos side rests upon two basal 

 plates, and joins the first and second azjgos radials upon the right and 

 the second, first radial upon the left, and curves over on the vault, 

 and is widel}^ cleft to the center where the free arm plates rest. 



The second first radial on the left of the azygos side rests upon two 

 basal plates, joins the first radial upon the left of the azygos side, and 

 the first and second posterior radials, and curves over on the vault, 

 and is widely cleft to the center, where the free arm plates rest. 



The posterior first radial rests upon two basal plates, joins the right 

 anterior first radial and the second, first radial on the left of the azj-gos 

 side, and supports upon its long arcuate upper side the second radial. 



The posterior second radial rests upon the posterior first radial, 

 joins one side to the ritiht anterior first radial, and another to the 

 second first radial on the left of the azygos side, curves over upon the 

 vault, and is widel}' cleft to the center, where the free arm plates rest. 

 The first az^'gos radial is a little smaller than the posterior first 

 radial, and rests upon two basal plates, joins the left and the right 

 anterior first radials, and supports upon the upper side the azygos 

 second radial. 



The az^^gos second radial rests its longer side upon the first azj'gos 

 radial; upon its leftside it joins the left anterior first radial and curves 

 over upon the vault; upon its right side it joins the right anterior first 

 radial and supports the azygos interradial plate. It is also cleft for 

 the support of the free arm plates, but the interradial plate forms one 

 side of the yoke-like opening, from the free arm plates to the smaller 

 plates covering the dome. 



The single interradial plate rests between the right anterior first 

 radial and the azygos second radial, and articulates with these plates 

 upon a serrated edge. It rises higher than the plates preserved in our 

 specimen, and curves toward the left anterior plate, while three phxtes 

 of the dome, in the direction to whicli its curvature points, stand upon 

 edge, showing quite clearly that the dome was possessed of a sub-cen- 

 tral proboscis on the azygos side. 



The plates covering the outer rim of the dome, commencing at the 

 three preserved plates of tlie base of tiie proboscis, on the left of the 

 azygos side, and extending around to tlie azygos interradial, are pre- 

 served in our specimen. The preserved plates, in this rim, form a row 

 from three to five wide, and show the dome very gradually arching 

 toward the proboscis. They are irregular and unequal in size, the 

 largest being about l-8th of an inch in diameter. 



The yoke-like cleft of each radial i)late, from the base of the arm to 



