ACTINOCEINID^. 601 



Remarhs. — The varioiis species which we refer to this genus were, with 

 a single exception, originally described imder AcHnocrinus ; but Meek and 

 Worthen, as we have already stated, placed them in a section by themselves. 

 The arms of these species are given off in a continuous row around the cnlyx 

 proper, and the bifurcation is on successive brachials beyond the distichals ; 

 while in Actinocrinus the calyx is more or less distinctly lobed, the arms are 

 given off in clusters, with large plates interposed between the rays, and the 

 bifurcation is on every second or third brachial. The structure of the pin- 

 nules also is essentially different in the two groups. 



In one very frail specimen of Caciocrimis proboscidalis,vfe were enabled to 

 examine the structure of the pinnules on all sides. At some places on the 

 ventral side the covering plates and side pieces were removed, and beneath 

 was exposed the floor of the food grooves, formed of two rows of small trans- 

 verse pieces, alternately arranged, and in a somewhat sloping position. The 

 structure is well shown by Mr. Westergren's excellent figures on Plate 

 LVIIL, Figs. 7ffl, b, c, cl. 



McChesney's Adimcrimis Jmrdiamis and A. Fosteri also belong to this 

 genus, but we are unable to identify the species from the descriptions and 

 figures. The types were lost in the Chicago fire. 



Cactocrinus proboscidalis (Hall). ' 

 Plate L VIII. Figs. 3, 4, 5, 6, 7a, I, c, d. 



1858. JcHnocrinns proboscidalis — Hall; Geol. Rep. Iowa, Vol. I., Part II., p. 584, Plate 10, Pig. 13. 

 1881. Actinocrinus proboscidalis — "W. and Sp. ; Revision Palffiocr., Part II., p. Ii5, 



SjQ. Actinocrinus qiiatermrius — 'E.LiA.; 1860, Siippl. Geol. Rep. Iowa, p. 22, and Whitfield 1893; 

 Mem. Am. Mus. Nat. Hist. N. York, p. 7, Plate 1, Pigs. 1-3. 



Sjn. A. excerptus Hall ; 1861, Descr. New Spec. Crin., p. 3 ; also Boston Journ. Nat. Hist. p. 276. 



Syn. A. quaternarius, var. spiniferns Hall; 1881, Descr. New Spec. Crin., p. 11. 



Syn. A. thernis Hall ; 1861, ibid., p. 11. 



Syn. A. lagena Hall; 1861, ibid., p. 13. 



Syn. A. dali/anus S. A. Millee ; 1881, Journ. Cincin. Soc. Nat. Hist., Vol. IV., Plate 7, Pigs. 1, \a. 



Calyx subovate, more or less truncate at the base. Ventral disk almost 

 as high as the dorsal cup, very gradually passing into the anal tube. Plates 

 of dorsal cup delicate, traversed by a single row of sharp, well defined ridges, 

 running from the edges of the plates to the centre, where they form con- 

 spicuous nodes, which upon the radials and brachials are transversely elon- 

 gate, but upon the interbrachials are subcircular and angular. 



Basal cup short, slightly spreading, excavated at the bottom ; the inter- 

 basal sutures deeply grooved. Radials larger than the costals, a little wider 



