152 PEOCEEDINGS OF THE ACADEMY OF 



rounded or somewhat flattened, as in Z. ramosus. If it were not for the fact 

 that the tjpical ?[>eeimen of Z. ramosi/s has the surface well preserved, we 

 would be led to think it might possibly have possessed 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, however, that it has the surface of its arms, second radi- 

 als 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 

 have never seen varieties of a species, in this or any of the allied groups, dif- 

 fering to this extent in such characters, we can but regard the ditferences as 

 being specific. 



It will be observed that the character of the arm and second radial pieces, 

 mentioned as distinguishing this species from Z. ramosus, also occur in the 

 species described in this paper under the name Z. scolind. That species, how- 

 ever, differs from this in having its first radials and subradial plates strongly 

 costate, while its arms are jjroportionally longer and ditt'er in being somewhat 

 serrated on each side. It also differs in having two arms, instead of only one, 

 from the anterior ray, as in this, and more divisions in its arms, which divisions 

 are given off at greater intervals. 



Locality and position. Burlington group, at Burlington, Iowa. Lower Car- 

 boniferous. Mr. Wachsmuth's collection. 



Zeacrinus LYRA, M. and W. 



Body short obconical, or expanding very rapidly from the column to the top 

 of the first radial pieces, where it is about twice as wide as high. Base not 

 concave but somewhat projecting, and about one-third as high as wide ; trun- 

 cated near three fourths its breadth by the slightly concave facet for the 

 attachment of the column. Basal pieces presenting a small pentagonal facet 

 above the column, two or three times as wide as long, with lateral margins so 

 short as to appear nearly triangular. Subradial pieces of moderate size, about 

 as wide as long, three hexagonal and two on the anal side heptagonal. First 

 radial pieces generally about twice as large as the subradials, near once and a 

 half as wide as long, and all pentagonal, with the upper side equaling the 

 entire breadth. Second radial pieces of very nearly the same size and form as 

 the first, though the fifth angle and sloping sides are of course above instead of 

 below; each supporting two arms, all around. Anal plates nearly all hexago- 

 nal, and, as usual, ari'anged in a double alternating series, the first resting 

 between the superior sloping sides of two of the subradials, under one side of 

 the first radial on the right, and connecting above the middle on the left, with 

 another resting on the superior truncated side of one of the heptagonal subra- 

 dials, and joining the first radial on the left. Above these the others extend 

 up to connect with the proboscis (so called). 



Arms all distinctly rounded, and after their origin on the second radial 

 pieces each bifurcating first on the fifth, sixth, seventh or eighth piece, above 

 which the outer division bifurcates (or gives off an arm en the inner side) 

 twice or three times at more or less nearly equal distances, all the inner arms 

 continuing simple throughout their entire length, and equaling the outer divi- 

 sions in thickness. Arm jjieces short and very distinctlj' wedge formed, each 

 having a moderately stout tentacle at its larger end, along the inner lateral 

 margins of the arms; axillary or bifurcating pieces a little larger than the 

 others, but not more convex. Tentacles composed of joints about twice as long 

 as wide. 



Body plates not convex, and merely separated by linear sutures, which are 

 not gaping even between the first and second radials ; entire surface more or 

 less granular. 



Height of body to top of first radials, about 0-25 inch ; breadth, about 0-50 

 inch ; length of arms, apparently nearly 2 inches. 



[July, 



