RHODOCRINID&. Pali 
crinus. S. A. Miller in 1889 added Lyriocrinus, and adopted Lyon’s name 
Goniasteroidocrinus in place of Ollacrinus. He amended this in the following 
year by leaving out the monocyclic Hadrocrinus, and adding Archeocrinus 
and Raphanocrinus. 
To the genera which we arranged under this family in 1885,* we add the 
genus Diabolocrinus, which we have proposed for a species that had been 
previously referred by us to Archaoerinus. 
The Rhodocrinide are nearest related to the Thysanocrinide, but are 
readily distinguished by the complete lateral separation of the radials f by 
the interradials ; the radials of the Thysanocrinidx being in lateral contact 
except at the anal side. The marked asymmetry in the ventral disk, so 
characteristic of the latter family, is not ob- 
servable in the Rhodocrinidx, in which the 
whole calyx, as a general rule, is remarkably 
symmetrical. 
The family has a great stratigraphic range, 
extending from the Lower Silurian to the 
middle of the Carboniferous and becoming 
extinct in the Keokuk group. The ancestral 
type is probably Archwocrinus in the Trenton 
group, of which Diabolocrinus is an offshoot. 
The evolution of these forms through Lyrio- 
crinus in the Niagara, Thylacocrinus and Ripi- Fie. 10. — Rhodocrinus. 
docrinus in the Devonian, to the profusely 
developed Rhodocrinus in the Carboniferous, is by easy gradations. Nor 
is the step from Rhodocrinus to the highly specialized Gilbertsocrinus a 
difficult one, because there are transition forms in which the characters of 
the two genera are toa great extent merged. ?aphanoerinus in the Trenton, 
and Anthemocrinus from the Upper Silurian of Gotland, apparently repre- 
sent variations toward the Thysanocrinide. 
The Rhodocrinidx are by far the most important dicyclic family of the 
Camerata, being composed of ten genera and fifty-four species, of which 
thirty-six are from America, and eighteen from Europe. 
* Revision, Part IL., pp. 96 to 99. (Proceed. Acad. Nat. Sci. Phila., pp. 318-321.) 
+ There is an occasional exception to this in the genus Zyriocrinus, where the radials are sometimes 
connected by a narrow strip, except at the anal side. This occurs quite frequently in Z. dacty/us from the 
Niagara of New York; while in Z. melissa, L. juvenis, and an undescribed Lyriocrinus trom Dudley, England, 
the radials are widely separated. 
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