ACTINOCRINID^. 611 



CactOCrinus ectypus Meek and WoETHBN. 

 Plate LVI. Fig. 10. 



1869. Strotocrinus edi/pus — M. and W. ; Proceed. Acad. Nat. Sci. PliUa., p. 159. 



1873. Strotocrinus ecti/piis — M. and W. ; Geol. Kep. Illinois, Yol. V., p. 353, Plate 7, Yig. 5. 



1S81. Actmocriiius ectypus — W. and Sp. ; Rerision Piilaeocr., Part II., p. Ii3. 



Calyx elono-ate, snbovate ; 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 costse, 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 costse. Eadials 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. 



Tijpe in the Museum of Comparative Zoology. 



Eemarlcs. — 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 m 

 a straight line with the radials and costals. The species has no connection 

 with Strotocrinus, but somewhat approaches Actinocrimts in having the rays 

 separated throughout their full length, but they are not lobed as in that 

 genus. 



