226 
SMITHSONIAN INSTITUTION 
Fig. 
3 - 
3a. 
3b. 
4 . 
5 . 
5 a- 
Fig. 6. 
7 - 
8. 
ITg. 
9 - 
ga. 
Fig. 10. 
loa. 
Fig. II. 
13 - 
14 - 
15- 
1 6. 
17 - 
i8. 
- PLATE 27 
(All figures natural size unless otherwise stated) page 
Myelodactylus ammonis Batlier 86 
A close coil, with stem tapering to a point ; cuneate interlocking columnals, with a cirrus 
from the broad end of each, converging to center completely enveloping the crown. 
X 3/2. 
The same seen from outer curve, showing the rapid taper of stem to narrow distal end; 
longitudinal sutures not visible. X 3/2. 
A similar specimen natural size, with hour-glass shaped columnals bearing a cirrus at each 
end, and lenticular, non-cirriferous ossicles interposed. 
The same from outer curve tapering to a point ; longitudinal sutures strongly developed. 
X 3/2- 
Similar specimen with alternate cuneate columnals. X 3/2. 
The tapering distal end. X 3/2. 
Form of the cuneate columnals in outline. 
A small specimen of similar type to last. X 3/2- 
Fractured specimen having paired cirri on alternate columnals. X 3/2. 
Inner view of fragment showing form and arrangement of columnals for the paired cirri, 
with lenticular ossicles interposed. X 3/2- 
Beech River formation; Decatur County, Tennessee. 
Myelodactylus convolutus Hall 86 
Specimen from St. Paul, Indiana, with close coil and beginning of broad curve of stem ; 
cirri not preserved, were paired at each end of successive columnals, as shown by the 
facets. 
Specimen from the typical locality, Lockport, New York, showing the cirri in place, one 
to each successive columnal. 
Fragment from inner side of curve, showing form and arrangement of paired cirri at 
each end of successive columnals. 
Laurel and Rochester formations. 
Myelodactylus brevis Springer 86 
A nearly complete coil tapering to distal end, with paired cirri as in preceding species. 
X 3/'2. 
Distal end of same, seen from outer curve. X 3/2. 
Beech River formation; Decatur County, Tennessee. 
Myelodactylus fletcheri (Salter) 86 
Specimen in author’s collection with the crown in place, which is detachable for inspection 
at all sides, showing that it has only 4 radii. X 2. 
b. Posterior and anterior views of crown; anal tube in a resting upon left shoulder of 
r. post. Rs, indicating its Pleterocrinid affinities. X 6. 
Wenlockiaii ; Dudley, England. 
Myelodactylus extensus Springer 87 
Large specimen with stem extended about 8 cm. beyond the close coil, nearly straight, not 
terminating in a point ; cirri on alternating cuneate columnals. 
Specimen with about 5 cm. of stem beyond deviation from close coil, and proximal reverse 
curve in view ; has paired cirri on hour-glass-shaped columnals. 
Another specimen with stem extension of about 6.5 cm., tapering near the end, and per- 
haps terminating in small roots ; columnals as in preceding specimen. 
Large specimen with unusually small c'ose coil, and loose coil partially restored, extended 
for about 12 cm. not yet terminated ; cirri paired on hour-glass columnals. 
Smaller specimen with much of extended stem broken off ; crown is seen following re- 
versed curve, calyx indistinct; cirri alternating on cuneate columnals. X 3/2. 
Large specimen with incomplete stem extension about 7 cm. ; polished section obtained by 
grinding down to the axial canal, showing the proximal coil, neck, and crown in out- 
line, with scattered cirri in some places ; probably has less than 5 rays. 
Specimen with only the close coil remaining, having tlie cirri complete converging in the 
center. 
Specimen from the Wenlockian at Dudley, England, with paired cirri in place at the close 
coil, and stem extended far beyond that region not yet diminishing distalwards. 
All except fig, 18 from Beech River formation, Decatur County, Tennessee. 
