ACTINOCRINID &. 611 
Cactocrinus ectypus Merx and Worruen. 
Plate LVI. fig. 10. 
1869. Strotocrinus ectypus —M. and W.; Proceed. Acad. Nat. Sci. Phila., p. 159. 
1873. Strotocrinus ectypus —M. and W.; Geol. Rep. Illinois, Vol. V., p. 358, Plate 7, Fig. 5. 
1881. <Actinocrinus ectypus — W. and Sr.; Revision Paleocr., Part II., p. 143. 
Calyx elongate, subovate; the ventral disk one fourth shorter than the 
dorsal cup. Plates of the cup moderately convex, a little angular in the 
centre, their surface traversed by radiating costa, which in sets of three 
pass from the middle to the sides of the plates, dividing their surface into 
numerous triangles, each of which includes-another one, but more obscure. 
Basals forming a slightly spreading cup, more than twice as wide as 
high, and with small nodes at the lower margin, one placed at the termina- 
tion of each of the cost. Radials about as wide as long, and nearly as 
large as both costals together. The second costal smaller than the first, and 
both wider than long. Distichals half the size of the upper costals. ~The 
outer palmars of each ray support a single arm, the inner ones two. Arms 
three to each main division, or six to the ray; their structure unknown. 
Anal plate longer than wide, followed by eight to ten plates, of which the 
two upper are small, and connected with the interambulacrals. Regular 
interbrachials: 1, 2, 2, 2, 1, the upper one separating the upper brachials of 
adjoining rays. Ventral disk subconical, slightly bulging, the summit passing 
gradually into the anal tube; the plates are rather large, more or less con- 
vex or tumid, and of uniform size. The posterior oral takes part in the anal 
tube, which is large and nearly central. Column apparently large; the nodal 
joints deeply dentate at their outer margins. 
Horizon and Locality.— Lower Burlington limestone ; Burlington, Iowa. 
Type in the Museum of Comparative Zodlogy. 
ftemarks. —The typical figure by Meek and Worthen is quite mislead- 
ing, being made from a crushed and much distorted specimen. In plump 
specimens the calyx is not depressed, as described by those authors, nor do 
the upper rows of brachials curve out horizontally, but lie almost in 
a straight line with the radials and costals. The species has no connection 
with Strotocrinus, but somewhat approaches Actinocrinus in having the rays 
separated throughout their full length, but they are not lobed as in that 
genus. 
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