BATOCEINID^. 493 



and the more extravagant form of the anal protuberance. A. WortJieni is a 

 much larger species, and its anal area throughout is perfectly flat. 



Agaricocrinus nodosus iieek and Worthen. 

 Plate XLIII. Fig. 9. 



1869. Meek aud Woethen ; Proceed. Acad. Nat. Sci. PLila., p. 167. 



1873. Meek and Woethen ; Geol. Rep. lUiaois, Vol. V., p. 397, Plate 10, Figs. 7a, i. 



Closely resembling A. excavatns, and perhaps a mere variety of that 

 species. It agrees with it in the general form of the calyx, the convexity 

 of the dorsal cup, and the form and arrangement of the basals and radials ; 

 the first costals, however, are somewhat shorter, and always quadrangular 

 owing to the greater length of the first interbrachials ; while the second cos- 

 tals for the same reason are generally octagonal. The latter plates, like the 

 first interbrachials, are larger, and their upper portions, which do not take 

 part in the basal concavity, are strongly convex or even nodose. Also the 

 first distichals, which next to the axillary costals constitute the largest plates 

 of tlie calyx, are decidedly convex, and so to some extent are the inter- 

 brachials of the second row, which are narrow and rise to a level with the 

 arm bases. Second distichals small and cuneate, not extending out to the 

 full width of the first, the outer ends being occupied by the succeeding arm 

 plate, which meets it from the opposide side. The posterior rays have 

 toward the anal side but one distichal, which is axillary, and supports 

 from each side a palmar. Arms twelve, not quite as stout as in A. exca- 

 vatus, and the anal process less protuberant. 



Horizon and Localiiy. — Ujiper part of the Upper Burlington limestone, 

 Pleasant Grove, Des Moines Co., Iowa. 



T/jpe in tlie Musemn of Comparative Zoology. 



Remarks. — This and the preceding species were placed by us in Part II. 

 of the Eevision (p. 112) with Agaricocrinus americaniis. with which they both 

 have close affinities. 



Agaricocrinus bullatus Hall. 



Plate XLI. Figs. Ba, h, c, d. 



1838. Hall; Geol. Eep. Iowa, Vol. I., Part II., p. 562, Plate 9, Figs. 11«, b. 



Sjn. Agaricocrinus pentagonm — Hall, 1860; Suppl. Geol. Hep. Iowa, p. 57; and TVliitfield, 

 Amer. Mus. Nat. Hist. N. York, 1893, Vol. I., p. 25, Plate 2, Figs. 17, 18. 



Of medium size. Calyx depressed pyramidal, distinctly pentangular 

 below the arm bases, and rather deeply concave at the bottom. The con- 



