FOSSILS OF THE BUKLIXGTOX GKOUP. 429 



long, and scarcely showing 1 any tendency to assume a wedge- 

 shaped outline; each one with a small pinched or angular 

 projection on the middle of the dorsal side, giving the arms 

 a subcarinated appearance; but these projections are not 

 continuous, being separated by notches at the sutures be- 

 tween the pieces, and a little inclined upward, so as to 

 impart to the dorsal side of the arms a serrated appear- 

 ance, as seen in an outline lateral view. Axillary pieces 

 at all the bifurcations of the arms larger than the other 

 arm pieces, and more prominent and angular. 



Surface of body plates nearly convex, or somewhat tumid, 

 and without costae or carina, Column verv small, round 







or subpentagonal. and composed near the base of nearly 

 equal, rather thin pieces, with a very minute central per- 

 foration. Sutures between the first and second radial 

 pieces widely gaping. 



Hight of body, 0.07 inch; breadth, about 0.22 inch; length 

 of arms, about 0.60 inch. 



In several respects this species agrees almost exactly with Z. ramoxux. 

 of Hall, which has the same proportions, with its arms bifurcating in 

 exactly the same way, and composed of similar short pieces, showing 

 no tendency to a wedge-formed outline. On comparison with the 

 original typical specimen of that species, however, now before us, the 

 species under consideration is found to differ in having its .second radial 

 pieces each provided with a sharp, strongly defined mesial carina, and 

 the surface on each side of the carina distinctly concave, instead of 

 having these pieces merely obtusely rounded. The same or a similar 

 difference is also seen in the arm pieces, each of which is provided with 

 one or more little projections on the dorsal side, instead of being 

 smoothly rounded or somewhat flattened, as i;i Z. ramosns. If it were 

 not for the fact that the typical specimen of Z. ramosus has the surface 

 well preserved, we would be led to think it might possibly have pos- 

 -d the sharp carina of the second radials, and the projecting points 

 of the arm pieces, seen in the species under consideration, and that 

 they might have been removed by accidental abrasion. The fact, how- 

 ever, that it has the surface of its arms, second radials and other parts 

 so well preserved as to show the original fine, delicate granulations 

 over the whole, demonstrates that it could never have possessed the 

 characters mentioned in the species we have here described : and as we 



