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ACTINOCRINID2. 601 
Remarks. — The various species which we refer to this genus were, with 
a single exception, originally described under Actinocrinus ; 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 calyx 
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 Cactocrinus proboscidalis, we 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. 7a, 4, c, d. 
McChesney’s Actinocrinus hurdianus and A. Foster: 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 (Hatz). ' 
Plate LVILL. Figs. 8, 4, 5, 6, Va, b; ¢, d. 
1858. Actinocrinus proboscidalis—-Hatn; Geol. Rep. Iowa, Vol. I., Part IL, p. 584, Plate 10, Fig. 13. 
1881. <Actinocrinus proboscidalis —W. and Sr.; Revision Paleocr., Part II., p. 145. 
Syn. Actinocrinus quaternarius —Hat; 1860, Suppl. Geol. Rep. Iowa, p. 22, and Whitfield 1893 ; 
Mem. Am. Mus. Nat. Hist. N. York, p. 7, Plate 1, Figs. 1-3. 
Syn. A. excerptus Hatt; 1861, Descr. New Spec. Crin., p. 3; also Boston Journ. Nat. Hist. p. 276. 
Syn. 4. quaternarius, var. spiniferus Hau; 1881, Descr. New Spec. Crin., p. 11. 
Syn. A. themis Hat; 1861, ibid., p. 11. 
Syn. 4. Jagena Hatt; 1861, ibid., p. 13. 
Syn. 4. dalyanus 8. A. Mitter; 1881, Journ. Cincin. Soc. Nat. Hist., Vol. IV., Plate 7, Figs. 1, 1a. 
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 
76 
