•150 PROCEEDINGS OF THE ACADEMY OF 



rasp-like appearance, which has suggested the specific name. The body plates 

 are also rendered very rough by a ridge extending from the middle of the up- 

 per edge of each first radial to connect \yith others on the subradials, and the 

 presence of other irregular asperities. Sutures between the first and second 

 radials widely gaping when the arms are folded together. Column of moderate 

 size, and composed of thin, nearly round pieces, with projecting rough edges, 

 and a rather small subpentagonal central perforation. 



Height of body to the top of the first radials, 0-10 inch : breadth, about 0-42 

 inch ; length of arms, about 170 inch. 



This species is related to Zeacrinus ])erangnlatus, of Dr. White, but differs in 

 having its arms longer and less tapering, as well as bifurcating more fre- 

 quently; also in having each inner division of each arm smaller than the 

 outer. The bifurcating pieces of its arras are likewise proportionally smaller, 

 and not protuberant as in that species. In the species perangulatus the arm 

 pieces are also merely angular along the middle, while in that under consider- 

 ation there is, instead of a continuous angle, a row, of little pointed isolated 

 protuberances, presenting a crenate appearance as seen in outline. 



Locali/i/ a7id position. Upper division of the Burlington group, Burlington, 

 Iowa. Lower Carboniferous. No. 321 of Mr. Wachsmuth's collection. 



Zeacrinus aspeb, M. and W. 



Body small, much depressed, or twice and a half as wide as high, broadly 

 truncated and concave below, the concavity including the base and about half 

 the length of each subradial piece. Base small and nearly or quite hidden by 

 the column. Subradial pieces very abruptly geniculated in the middle, the 

 lower or inner half forming a part of the concavity of the under side, and the 

 upper a part of the outer wall of the bodj^, while their prominent middle forms 

 the margin of the concavity below, each presenting a pentagonal outline, ex- 

 cepting one on the anal side, which is hexagonal. First radial pieces about 

 twice as long as the subradials, and twice as wide as long, all pentagonal in 

 form, with the upper truncated side equaling the full breadth. Second radial 

 pieces as wide and once and a half as long as the first, pentagonal in form 

 (unless the anterior one, which has not been seen, may be an exception), and 

 supporting the arms on their superior sloping sides, each with a very promi- 

 nent sharp carina extending up the middle, while the surface on each side of 

 the carina is deeply concave, excepting at the lower margin, along which there 

 is also a transverse ridge or carina. 



Anal plates arranged as iu the last described species, in a double alternating 

 series, the lower one being placed obliquely under one side of the first radial 

 on the right, while the next rests upon a short end of one of the subradials, 

 the two connecting together and supporting the others above. 



Arms, after their origin on the second radial pieces, each bifurcating on the 

 fcixth piece, the two divisions of each being of equal size, but the inner one is 

 simple, while the outer bifurcates again on the sixth, seventh, eighth or ninth 

 piece above the first division, beyond which the two equal divisions are 

 simple as far as the}' can be traced in the specimens examined. Arm pieces 

 short, or nearly twice as wide as long, wedge form, and each strongly project- 

 ing on the longer side, alternatelj-, so as to present a zigzag appearance ; bifur- 

 cating pieces all larger than the others, and extending out, on the dorsal side 

 of the arms, into pointed prominences, sometimes assuming the character of 

 short spines, which, with the lateral processes of the other pieces, give the 

 arms a very rough, harsh appearance. 



Surface of the body plates with deep excavations at the corners, and strong 

 ridges or cariufe between the excavations. Of these carina?, two descend di- 

 verging from the middle of the upper side of the first radials (along which 

 there is also a transverse ridge), to connect with others on tlie subradial 

 pieces. Sutures between the first and second radial jiieces very widely gaping. 

 Column round and very slender near the base, where it is composed of pieces 



[July, 



