NATURAL SCIENCES OF PHILADELPHrA. 311 



they spring, and sometimes tliemselves bifurcate once or twice; 

 divisions composed of pieces about as long as wide. 



First anal piece nearly as large as one of the smaller subradials, 

 resting on the superior truncated edge of the largest heptagonal 

 subradial, between the first radial on the left and the first and 

 second on the right, while it supports others above that form the 

 base of the ventral extension. Interradial pieces with the lowest 

 piece of the ventral part resting between the truncated superior- 

 lateral angles of the first primarj^- radials so as to appear as 

 minute interradials. Surface without costceor sculpturing of any 

 kind. 



Yentral extension ver}' long, or nearly or quite equalling the 

 length of the arms, and as wide as the bod}^ below ; composed of 

 the usual small hexagonal plates apparently without costse, and 

 separated by punctured sutures. Column slender, slightly tapering 

 downward just below the base, near which it is more or less pen- 

 tagonal, and composed of short alternatel}^ thicker and exceed- 

 ingly thin segments. Farther down, it becomes nearly or quite 

 cylindrical, and composed of more uniform very short pieces, 

 with a very small nearly or quite round perforation. 



Length of body, from the lower end of base to the top of first 

 primary radials, 0.24 inch; breadth of do., at top, 0.16 inch; 

 length of rays, from top of body to first bifurcation, 0.20 inch ; 

 length of arms, above this bifurcation, 2.30 inches ; diameter of 

 column, 0.04 to 0.05 inch. 



This delicate little species seems to agree exactly, in structure 

 as well as in physiognoni}^, with Dendroa-inus^ excepting that it 

 appears to have the small pieces forming the lower part of its 

 ventral extension above the first anal piece, and those seen in the 

 interradial spaces above the large first radials that form a part of 

 the walls of the body, connecting laterally with the succeeding 

 smaller radials, nearly or quite up to the first bifurcation. This 

 arrangement, if it really exists, would make these smaller primary 

 radials, above the body proper, as it were, a part of the walls of 

 the body or ventral extension; so that the rays would only become 

 free at the first bifurcation. The specimens seen are not in such 

 condition as to remove all doubts on this point; but, in some con- 

 ditions, these little pieces between the rays give that part of the 

 fossil somewhat the appearance of a Glyptocrinus. The presence 

 of well-developed subradials and a long ventral extension of the 

 1872.] 



