232 
SMITHSONIAN INSTITUTION 
PLATE 30 
(Figures natural size unless otherwise stated) 
Halysiocrinus dactylus (Hall) 123 
Fig. I. The type specimen, anterior view. Mus. Comp. ZooL, Harvard. 
2. Ant. view of free crown in author’s collection, with main ramus of axil-arms branching 
from nodose axillaries 2 and 3 times at intervals of 3 and 4 brachials ; ant. R. extend- 
ing far around towards anal tube. 
2a. L. ant. view of sam.e, showing median arm branching twice, proportions of lateral radials 
and separated segments of 1 . ant. R. 
2 h. Post, view of same ; hinged base closed against RR ; inferradials of vanished arms inter- 
posed between large RR, and m.eeting below anal .v, forming part of base of tube. 
3, 3a. A very young specimen probably of this species ; crown with complete stem, 2 opposite 
views, enlarged ; shows calyx higher than wide, narrowing downwards ; 1. post, view 
shows only one axil-arm and anal tube, and ant. view shows 2 arms and tube. X 2. 
Upper Burlington limestone ; Burlington, Iowa. 
Halysiocrinus perplexus (Shumard) 123 
Figs. 4, 5. L. ant. views of calyx, showing the hinge between radials and basals in position as they 
would be when fully extended; composed from weathered specimens with the two 
elements separate ; markings of muscular attachment seen in the fissure, and different 
tubercular ornament upon the surface. 
6. Another specimen similarly composed, seen from the interior, showing the same structures 
from the opposite side ; marks of muscular attachment at inner surface of RR and 
BB ; edges of opposing plates rounded ; articular faces of median and lateral arms 
are shown, and the cavity which lodged the viscera. 
7. Post, view of specimen with BB partly closed, their edges rounded, and showing arrange- 
ment of RR from the interior. 
8. 9, 10. A series of radials to show the change in form with age from elongate with nearly 
parallel sides to relatively short and widely spreading downwards. 
II, 12, 13. A series of bases seen from the interior. 
New Providence shale, basal Mississippian ; Button-mould Knob, Kentucky. 
Fig. 14. 
Halysiocrinus 
Post, view of calyx, with basals closed ; 
16. 
i6a. 
20, 21 
nodosus (Hall) 124 
gainst the lateral radials which have extended 
around to the anal series ; inferradials of vanished arms now meeting between them 
and below anal .r, and indented by stem. 
Crown with the hinged basals widely opened until the stem is almost in line with the 
median arm ; bifurcations of main branch of axil-arms well shown. 
L. ant. view of crown, giving direct view of bifurcations of median arm to about 10 finials. 
Post, view of same, with hinged basals tightly closed against radials, inferradials of 
vanished arms meeting below anals and Indented by stem; anal plates but little visi- 
ble at base, but tube projects at distal end. 
A typical complete crown in “ humped ” position recumbent upon the stem, with semi- 
elliptical outline; median arm bifurcates on 6th brachial, and axil-arms at intervals 
of 3 and 4. 
A larger specimen in similar position, with stem underneath ; showing the complete 
branching of the median arm on 7th brachial to a total of 10 finials. 
A large crown closely recumbent upon tbe stem, with arms partly overlapping it. Main 
branch of axil-arms well exposed in the last five specimens. 
Ant. and 1 . post, views of two young specimens with elongate calyx, only 3 axil-arms, 
and median arm branching once and twice. 
Keokuk shale, Mississippian; Indian Creek, Indiana. 
