590 GEOLOGICAL SURVEY OF IOWA. 



the other two heptagonal. Third range consisting of four 

 small plates ; above which are two or three small irregular 

 plates lying between the bases of the arms. 



ARMS consisting of a double series of short plates, slightly 

 interlocking by their obtusely wedgefonn faces, and furnished 

 with long jointed tentacula. Proboscis extremely elongated 

 [ that of the specimen figured measuring more than three 

 inches, and still imperfect at the extremity]. Column round, 

 consisting of thick joints with rounded margins and inter- 

 mediate thinner joints. 



This species, though bearing some resemblance to A. turbinaius, var. elegans, is 

 nevertheless distinctly marked by the convexity of its sides, stronger calyx, larger 

 and differently arranged plates, less number of arms, and longer proboscis. 



Fig. 2. A specimen somewhat crushed, but preserving the arms, a large part of the 

 proboscis, and a portion of the column. 



Fig. 2 a, b ( 4 c, 4 d, by error on some plates). Posterior and postero-lateral views 

 of another specimen without arms, column or proboscis. 



FIG. 88. 





The accom P an y in g diagram il- 

 l ustrates tne structure of this spe- 



cies> which is one of the most sim " 



p!e and uniform of those possessing 

 the supraradial plates; the ante- 

 TIOT ra y being like the more simple 

 forms of the genus, with no supra- 

 radial plates, and only two or 

 three brachials intervening between 

 the third radial and the arm- 

 plates. 



Geological formation and locality. In the Burlington limestone : Burling- 

 ton, Iowa. 



Actinocrinns umbrosus ( n. s.). 



PLATE XI. FIG. 3 a, b. 



BODY urnshaped, with the summit depressed-convex, the 

 margins spreading from below towards the base of the arms 

 nearly rectangularly to the direction of the axis ; base di- 



