86 
SMITtlSONIAN INSTITUTION 
Myelodactylus ammonis (Bather) 
Plate 2^1, figs, i-ga 
Herpetocrinus ammonis Bather, Crin. Goth, 1893, p. 49, pi. 2, figs. 54-63. — Myelodactylus ammonis Springer, 
Unusual Forms, 1926, p. 10, pi. 2, figs. 1-9. 
Coil very close; stem short, tapering to a point; cirri short, alternating 
from broad end of successive columnals. 
Beech River formation; Decatur County; and Waldron shale; Newsom, Tennessee. 
M. gorhyi Miller and Gurley, 17th Rep. Indiana Dep. Geol., 1891, p. 72, from near Nashville, 
Tennessee, is too indefinite for comparison. 
Myelodactylus convolutus Hall 
Plate 2j, figs. 6-8 
Myelodactylus convolutus Hall, Pal. New York, 2, 1852, p. 192, pi. 45, figs. 5, 6. — 'Springer, Unusual Forms, 
1926, pp. 8, 16, pi. I, figs. 1-8. — Herpetocrinus convolutus Bather, Crin. Goth, 1893, p. 48, ph 2, 
figs. 50-53. 
Coil open and broadly convolute distalwards; stem long; columnals short, 
quadrangular, uniform ; cirri flat, regularly paired on successive columnals. 
Rochester shale; Lockport, New York; Laurel limestone, St. Paul, Indiana; and other 
Silurian horizons and localities. M. bridgcportensis S. A. Miller, Jour. Gin. Soc. Nat. Hist., 
1880, p. 141, figs. 2a-e, from the Racine dolomite, and Eomyelodactylus rotimdatus Foerste, 
Bull. 19, Sci. Lab. Dennison Univ., 1919, p. 19, pi. i, fig. 8, pi. 2, fig. 3 are thought to belong 
to this species. 
Myelodactylus brevis Springer 
Plate 2^, figs, g, ga 
springer. Unusual Forms, 1926, p. 10, figs. 9, 9a. 
Like eonvolutus , but with coil close and stem short, tapering to a point. 
Beech River formation; Decatur County, Tennessee. 
Myelodactylus fletcheri (Salter) 
Plate 21, figs. lo, loa, b 
Herpetocrinus fletcheri Salter, Catah Camb. Sih Foss., 1873, p. 118. — Bather, Crin. Goth, 1893, p. 46, ph i, 
figs. 34-49, and p. 182, under fig. 38. — Myelodactylus fletcheri Springer, Unusual Forms, 1926, p. 10, 
ph I, figs. 10-12C: 
A species from the Wenlockian of Dudley, England, and occurring also in 
Gotland. Similar to M. convolutus, but with cirri round and bead-like. The 
specimen figured is notable for being the only one of the genus from the Silurian 
which shows the exact structure of the crown, of locrinid type, with only 4 rays. 
It was noticed in Bather’s work of 1893, on p. 182. 
