HEXACRINIDZ. T79 
difficult to make comparison with allied forms. The descriptions of this and 
the two preceding species are made after Miller, we having no authentic 
specimens for comparison. 
CAMPTOCRINUS W. and Sp. (nov. subgen.). 
(kaumrrds pliant, xpivoy a lily.) 
In the construction of the calyx and arms identical with Dichocrinus, but 
differing in the structure of the stem, which in all the specimens in which 
we observed it is curled around the crown. The stem joints are circular 
near the calyx, but at some distance off gradually turn into crescent-shaped, 
and the two horns of the crescent give off long, stout, and pliant cirri from 
every joimt. The stem coils to the concave side. 
The structure of this stem reminds us of Hall’s genus Myelodactylus * of 
the Niagara group; and similar stems occur in the Wenlock limestone of 
Dudley, England, and Gotland, Sweden, which have been referred by Angelin, 
and also by Bather, to the inadunate genus Herpetocrinus Salter, a genus 
with close affinities to Heterocrinus. Such stems are also found among the 
Poteriocrinde of the Kaskaskia group, showing that they occur not only at 
various horizons, but also in very different groups; and we doubt if this 
structure is of much importance for classification. We therefore place Camp- 
tocrinus subgenerically under Dichocrinus. 
Mistribution. — Found from the Keokuk limestone to the Kaskaskia group, 
and apparently restricted to America. 
Type. — Camptocrinus myelodactylus. 
Camptocrinus myelodactylus W. and Sp. (nov. spec.), | 
Plate LX XV. Figs. 1, 2a, b. 
A small species with curving stem and long paired cirri, which are given 
off in longitudinal rows on the concave side, as in Hall’s Myelodactylus. Calyx 
elongate, slightly spreading; the plates smooth; the suture lines indistinct. 
Base one third the height of the dorsal cup, its sides convex. Radials twice 
as long as wide; the facets not excavated, and the costals resting upon the 
straight upper faces, occupying three fourths their width. Costals two, very 
short; the second obtusely angular above. Arms two to the ray, in close 
contact laterally, twice and a half as long as the calyx, and composed of 
* Paleont. N. York, Vol. IT., p. 232, Plate 42, Figs. 5, 6, and Plate 45, Figs, 7, 8, 9. 
