76 PROCEEDINGS OF THE ACADEMY OP 



with the pseudo-brachial appendages composed, near the body, of a double al- 

 ternating series of pieces, and bifurcating farther out into two rounded branches, 

 composed each of a single range of pieces pierced by a small central canal), 

 the species under consideration will be readily distinguished by its much 

 longer and more slender pseudo-brachial appendages, which have their pieces 

 merely rounded and finely granular, instead of being each provided with a 

 row of small tubercles around the middle. From G. tuberculosus, Hall, (sp.), 

 which, if correctly identified among the specimens before us, has its pseudo- 

 brachial appendages constructed, at the base at least, in the same way, it will 

 be distinguished by having its subradial pieces produced into short pointed 

 spines, instead of being merely tuberculiform. The same character, as well 

 as its larger size, and more robust appearance, will also distinguish it from 

 our G.fiscellus and G. reliculatus, Hall (sp.) 



The specimen is too much crushed to afford measurements of the body, but 

 the false arms measure 60 inch from the body out to the point of bifurcation, 

 and 0.35 inch in breadth. Each of the branches near the point of bifurca- 

 tion measures only 0-18 inch in thickness, while one of them can be traced 

 to a length of 2 inches, where it is broken off, and measures 0-13 inches in 

 thickness, the whole length of each branch being probably not less than three 

 inches. 



Locality and Position. Lower division of the Burlington group, Burling- 

 ton Iowa. Lower Carboniferous. No. 308 of Mr. Wachsmuth's collection. 



GONIASTEROIDOCRINUS OBOVATUS, M. and W. 



Body rather large, truncato-obovate, being narrow below, with convex sides, 

 and truncated above ; height a little greater than the breadth. Base small, 

 and very deeply concave; basal pieces entirely within the concavity of the 

 under sides, and hidden by the column, when it is attached ; apparently com- 

 pletely inverted by the pushing in, as it where, of the column, around which 

 they are folded down with their outer sides inward, while their edges that join 

 to the subradials are turned downward. Subradials of moderate size, very 

 tumid or tuberculiform, but not pointed; curving into the concavity below 

 and upward at the outer ends, while their tumid central part forms the base 

 upon which the body stands when placed upon a plane surface; all heptagonal 

 in form, if we count an obtuse angle at the middle of the base of each. 

 First radial pieces about as large as the subradials, tumid, and of nearly equal 

 length and breadth ; all heptagonal in outline. Second radial pieces generally 

 smaller than the first, and proportionally a little narrower, rather tumid, and 

 all hexagonal in form. Third radial pieces of about the same size as the 

 second, or sometimes slightly larger, equally convex, pentagonal or hexagonal 

 in outline, and each supporting on their superior sloping sides, convex second- 

 ary radials, the second of which is sinuous above, so as to form the under side 

 of the openings to which the pendent true arms connect, while on their outer 

 sloping sides they connect with a series of small pieces, which unite with others 

 coming in the same way from the adjacent ray, so as to form the under side of 

 the base of the false arms over each intcrradial and anal space. 



Anal and interradial areas of an oval outline, and scarcely distinguishable 

 from each other, each occupied by twelve to fourteen more or less convex, or 

 tumid pieces, the first of which is hexagonal, about as large as the second 

 radials, and rests as usual on the upper truncated side of a subradial ; above 

 these there are usually three arching ranges of three each, and three or four 

 other pieces still farther up, more or less irregularly arranged. 



Vault flat, not quite equaling the greater breadth of the body below, and 

 composed of irregular tumid pieces, generally of rather small but unequal 

 sizes, with a more or less marked depression opposite each false arm ; opening 

 apparently nearly central. False arms composed at their bases of four rows 

 of small pieces above and two below, arranged so as to inclose two distinct 

 canals which do not pierce any of the pieces themselves. 



[April, 



