ACTINOCRINID ZA. 609 
the plates of one series stand obliquely to those of the opposite one, the 
outer ends of the plates directed slightly downward. Each plate, close to 
the upper margin, is marked by a sharp, conspicuous transverse ridge, while 
the lower parts of the plates are beautifully corrugated. The transverse 
ridges, which somewhat resemble the teeth of a file, suggested the specific 
name. Pinnules long; the dorsal side of each joint armed with a sharp, 
curved spine. Regular interbrachials: 1, 2, 2. Anal plate followed by 
2, 2, 2 plates, and these by two very minute pieces, placed within the arm 
regions. Interdistichals one, large. Ventral disk depressed conical, com- 
posed of comparatively few large plates, the centre of which is produced 
into a small slender spine. Anal tube. moderately large, and almost 
central. 
Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 
Type in the University Museum at Ann Arbor. 
Liemarks. — Differing from all other Burlington species of this genus in 
the surface markings of the arms. The set of arms figured by Whitfield 
(Mem. Am. Mus. Nat. Hist. N. York, Plate 1, figs. 8 and 9) as of this species, 
in our opinion belongs to Actinocrinus tenuisculptus McChesney; they do not 
show the sharp file-like ridge of each joint, which is so characteristic of this 
species. 
Cactocrinus longus (Mrex and Worruey). 
Plate LVII, Fig. 8. 
1869. <Actinocrinus longus — Mux and Wortuen; Proceed. Acad. Nat. Sci. Phila., p. 156. 
1873. Actinocrinus longus— Muzx and WortHEN; Geol. Rep. Illinois, Vol. V., p. 345, Plate 8, 
Figs. la, 6. 
1881. <Actinocrinus longus —W. and Sr.; Revision Paleocr., Part II., p. 144. 
A large and elongate species. Calyx to the base of the anal tube 
almost once and a half as high as wide. Dorsal cup somewhat shorter than 
its width across the arm bases, the sides a little convex. Plates rather 
thin, very slightly elevated, and in well preserved specimens ornamented 
with very fine, more or less obscure ridges, which in sets of from one to five 
pass from plate to plate. The basals, radials, and costals are traversed by 
five such ridges; five others proceed to adjoining radials and the anal plate, 
but only three from the costals and radials to the lower interbrachials, and 
from the costals to the distichals, while all the remaining plates have single 
ridges. The suture lines, except the basi-radial and interradial ones, rarely 
observed. 
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